If there are indeed nine segments from each season, and future sets continue to focus on the same years, then I wonder if the sets will continue to have bonus skits grouped by season or perhaps a theme. Some good ideas could be the alphabet (there are 26 letters, there could be three groupings of nine skits for each letter, and it could start with a segment about the alphabet to fill 27), number skits (there could be nine, for the numbers 1-9), monster skits, game show skits, parody skits, character skits News Flash skits, and so on.
Volume two could have the bonus skits done like this: The alphabet and letters A-H, the letters I-Q, the letters R-Z, the numbers 1-9, and main characters (an Ernie and Bert skit, a Cookie Monster skit, a Grover skit, an Oscar the Grouch skit, a Count skit, a Guy Smiley skit, a Roosevelt Franklin skit, a Big Bird skit, a Herry Monster skit, and a Kermit the Frog skit).