I don't understand where you are coming from. GAINAX doesn't have to do anything, its Annos decision on Eva. He said it before he wasn't going to work on a sequel to Eva. And besides.... like every other anime show (successful or not) Eva has been forgotten in Japan (or mostly), and unless we see a shift in Anime markets in the near futere (not likely) Japanese fans rule anime decisions. And besides.... with the third impact over, the Evas and Angels gone.... how would you come up with a sequel? Unless we are talking about AU crap... its just not doable, like with Cowboy Bebop and many other series.
after i think about it, if Anno released a sequill it would probly suck. you were right when you said evas,angels, gone everyone got on with there lives. maybe Anno released the renwal because there was just now way for a good sequill. so after the renewall project and the live action film eva will be forgotten. unless you like eva_R if your into that sort of thing(i am).