Honestly, after watching Shakugan no Shana i dont really care if they're going to make 3rd season of it first(it's already listed on Mal). Only thing i disliked was Railgun, if they're going to make 2nd season, i hope they will show us something about Misaka's clones.
they have to, i don't think there is anything else to show in the manga.
but i would love to see Toaru Jihanki no Fanfare animation :))
also as a fillers, gap closer between Misaka destroying lab, and Touma helping her we can have one or two of SS:
Toaru Kagaku no Railgun SS: Liberal Arts City ?
Toaru Kagaku no Railgun SS2: Shopping Mall Demonstration ?