Surprised no one's mentioned this yet. The expansion's been announced. Things known so far...

• 2 new characters, Tsubaki and Hazama.
• Nu-13 has been replaced by Lambda-11.
• All stages have been redone to some degree.
• Everyone's had some tweaks to gameplay, with Rachel, Nu/Lambda, and Arakune being majorly nerfed.
• Projectiles are marked to make it easier to identify them as such.
• The game takes place several days after the old one.
• Barrier Bursts now work different
• Guard Libra has been replaced by a new system.
• Taokaka has a larger chest.

Tao's larger chest is art only.

And Aksys pretty much confirmed at least 3 if not 4 new characters

DaiAndOh said:

And that it's stand-alone and not DLC.

dshaffer said:

Will she refer to herself as Neo Boobie-lady?

Tao: "...Tao is Tao. The Booby Lady is the booby lady. Now give me food"
I figure any discussion about her increased chest size would result in a similar dialogue.