Although I don't intend to do an E11.5 or anything, I will be taking my time with 12. Here are my general goals:
Gotta get them Shiny Sprites done fixed up
Need to finish Mega sprites
Not to mention shiny mega sprites ahwmahgad
Also the sprites for the PUL- I, sorry, what?
Going to try and make existing field effects more readable (i.e so players know when a move is used that gains bonus power, among other things-- Radomus' Chess field currently does this and it works a lot better than the other ones)
Need to get scripting support to change the displayed background mid-battle
So that we can make new field effects! Including transformative ones (such as burning grassy field)
Finally, all that scripting and spriting stuff aside, E12 just takes place over a large area, a lot of which will require custom graphics, mapping and development time. So as it is, I can't offer any specific date.