Announced March 12th:

The Postal Service honors Sesame Street as one of the most influential and beloved children’s television shows. For the last 50 years, it has provided educational programming and entertainment for generations of children throughout the country and around the world. The stamp art features photographs of 16 Muppets from Sesame Street — Big Bird, Ernie, Bert, Cookie Monster, Rosita, The Count, Oscar the Grouch, Abby Cadabby, Herry Monster, Julia, Guy Smiley, Snuffleupagus, Elmo, Telly, Grover and Zoe. Art Director Derry Noyes designed the stamps.

No date or first-day city were given. Further updates will appear below, in order announced.

According to Wikipedia, “Sesame Street” debuted on November 10, 1969. The show’s 50th anniversary press release says 50th-anniversary episode is planned for November 2019. The show’s website also has an anniversary page.

Updated May 23rd:

[press release]
Sesame Street Stamps
Iconic Show’s 50th Anniversary Celebrated by the U.S. Postal Service

What: The U.S. Postal Service honors Sesame Street, the influential and beloved children’s television show. For 50 years, the series has provided educational programming and entertainment for generations of children throughout the country and around the world.

The first day of issue event for the Sesame Street Forever stamps will be held immediately preceding one festival stop on the Sesame Street Road Trip, a celebration of the show’s golden anniversary that will be held in 10 cities across the United States. News of the release is being shared on social media with the hashtag #Sesame50.

When: Saturday, June 22, 2019 at 9:30 a.m. EDT

Where:
Lafayette Park
1592 Antietam Avenue
Detroit, MI 48207

RSVP: RSVP required for attendance at: www.usps.com/sesamestreet
Space is limited.

Background: The first episode of Sesame Street aired on Nov. 10, 1969. From the beginning, Sesame Street was like no other children’s program. Human characters, often children themselves, interacted with the Muppets of Sesame Street.

Arranged in horizontal rows, the stamps showcase 16 of the Muppets characters that appear on Sesame Street — Big Bird, Ernie, Bert, Cookie Monster, Rosita, The Count, Oscar the Grouch, Abby Cadabby, Herry Monster, Julia, Guy Smiley, Snuffleupagus, Elmo, Telly, Grover, and Zoe. Images of nine of the characters appear on the right side of the pane underneath the iconic Sesame Street sign. The back of the pane displays the Sesame Street 50th anniversary artwork.

Sesame Street stamps are being issued as Forever stamps. Forever stamps will always be equal in value to the current First-Class Mail 1-ounce price.

All postage stamps are available for purchase at Post Offices locations, online at usps.com and by toll-free phone order at 1-800 STAMP-24.

From the June 6th Postal Bulletin:

On June 22, 2019, in Detroit, MI, the United States Postal Service® will issue the Sesame Street stamps (Forever® priced at the First-Class Mail® rate) in 16 designs, in a pressure-sensitive adhesive pane of 16 stamps (Item 479500). The stamps will go on sale nationwide June 22, 2019, and must not be sold or canceled before the first-day-of-issue. The Sesame Street pane of 16 stamps may not be split and the stamps may not be sold individually.

In 2019, the Postal Service™ honors Sesame Street, the influential and beloved children’s television show. For the last 50 years, Sesame Street has provided educational programming and entertainment for generations of children throughout the country and around the world. The stamp art features photographs of 16 of the Sesame Street muppets:

• Row 1: Big Bird, Ernie, Bert, and Cookie Monster.
• Row 2: Rosita, The Count, Oscar the Grouch, and Abby Cadabby.
• Row 3: Herry Monster, Julia, Guy Smiley, and Snuffleupagus.
• Row 4: Elmo, Telly, Grover, and Zoe.

Images of nine of the characters appear on the right side of the pane underneath the iconic Sesame Street sign. The back of the pane displays the Sesame Street 50th anniversary artwork. Art director Derry Noyes designed the stamps.

Availability to Post Offices: Item 479500, Sesame Street (Forever Priced at the First-Class Mail Rate) Commemorative Pane of 16 Stamps : Stamp Fulfillment Services will make an automatic push distribution to Post Offices of a quantity to cover approximately 30 days of sales.

How to Order the First-Day-of-Issue Postmark:
Customers have 120 days to obtain the first-day-of-issue postmark by mail. They may purchase new stamps at their local Post Office™ or at The Postal Store® website at usps.com/shop. They must affix the stamps to envelopes of their choice, address the   envelopes (to themselves or others), and place them in a larger envelope addressed to:

FDOI – Sesame Street Stamps
USPS Stamp Fulfillment Services
8300 NE Underground Drive, Suite 300
Kansas City, MO 64144-9900

After applying the first-day-of-issue postmark, the Postal Service will return the envelopes through the mail. There is no charge for the postmark up to a quantity of 50. There is a 5-cent charge for each additional postmark over 50. All orders must be postmarked by October 22, 2019.

Technical Specifications:

Issue: Sesame Street Stamps
Item Number: 479500
Denomination & Type of Issue: First-Class Mail Forever
Format: Pane of 16 (16 designs)
Series: N/A
Issue Date & City: June 22, 2019, Detroit, MI 48233
Art Director: Derry Noyes, Washington, DC
Designer: Derry Noyes, Washington, DC
Typographer: Derry Noyes, Washington, DC
Modeler: Joseph Sheeran
Manufacturing Process: Offset
Printer: Ashton Potter (USA) Ltd. (APU)
Press Type: Muller A76
Stamps per Pane: 16
Print Quantity: 62,000,000 stamps
Paper Type: Nonphosphored Type III, Block Tag
Adhesive Type: Pressure-sensitive
Processed at: Ashton Potter (USA) Ltd. (APU)
Stamp Orientation: Vertical
Image Area (w x h): 0.73 x 1.05 in./18.542 x 26.67 mm
Stamp Size (w x h): 0.91 x 1.19 in./23.114 x 30.226 mm
Full Pane Size (w x h): 6.96 x 5.2 in./176.784 x 132.08 mm
Press Sheet Size (w x h): 14.045 x 26 in./ 356.743 x 660.4 mm
Colors: Black, Cyan, Magenta, Yellow
Plate Size: 240 stamps per revolution
Plate Number: “P” followed by four (4) single digits
Marginal Markings:
Front: Header: “Sesame Street Logo” • Plate number one corner
Back: Sesame Street — 50 Years and Counting logo • ©2019 USPS • USPS logo • two barcodes (479500)
• Promotional text • Plate position diagram

Here are the first-day postmarks for this issue:The Digital Color Postmark measures 2.98″x1.41″The B&W pictorial measures 2.41″x1.44″

Updated August 7th:
Here are the Scott catalogue numbers for this issue:
5394 pane of 16
a. Big Bird
b. Ernie
c. Bert
d. Cookie Monster
e. Rosita
f. The Count
g. Oscar the Grouch
h. Abby Cadabby
i. Herry Monster
j. Julia
k. Guy Smiley
l. Snuffleupagus
m. Elmo
n. Telly
o. Grover
p. Zoe