So I just got the patch (but haven't gotten my Mewtwo codes...). I can confirm the set of normal 8-player smash stages is the same, but it seems like there are more omegas available now? Literally the only six you can't pick are Final Destination, the new Mario Circuit, Skyloft, Coliseum, Boxing Ring, and Wuhu Island. This is true whether you have a full 8 players or just 6. I could swear there were fewer before, but I don't have a list of previously legal 8-player omegas handy.
Yep, more were added. The details I found from a helpful guy on anothe forum.
3DS
Note: Replay data that is saved in the game prior to the patch update will no longer be playable after the update.
– Added a new functionality for purchasing DLC
– Adjustments have also been made to balance the game and make for a more pleasant gaming experience.
Wii U:
– Users will be able to purchase DLC from Nintendo eShop.
– Share mode has been added:
– Users will be able to post photos, replay data, Mii Fighter data, and Custom stage data to the official server to share with other users around the world. Users will also be able to search and download the content as well
*Users can only post their own content. Content posted to the server will be deleted after 30 days.
– Users will be able to post photos and Custom stages to Miiverse from within the game (Photos will be posted to the official Snapshot Sharing Community and Custom stages will be posted to the official Stage Sharing Community
– Users can download data from the server to Super Smash Bros. for Wii U if there is an activation button in the images posted on Miiverse.
– Users will be able to share and exchange photos, replay data, Mii Fighter data, and Custom stage data with users on their Nintendo 3DS Friend List.
• Content will be received when the Nintendo 3DS is connected to the Internet
• It may take some time to receive the data
• Content uploaded to the server will be deleted from the server after 30 days.
– Added 6 new 8-Player Stages
– Omega Stages:
• Delfino Plaza
• Port Town Aero Dive
• Woolly World
• Orbital Gate Assault
• Wii Fit Studio
• Pilotwings
– Adjustments have also been made to balance the game and make for a more pleasant gaming experience.