James L. Brooks says:
THR: Are you doing another [Simpsons feature]?
Brooks: We always say, television first. We love the season we are having right now — we really feel good about it. But we’re open to it, and we sort of have half a notion.
THR: Does that mean you’re developing a script?
Brooks: No. When we say we’ll do it, we commit. We go all the way, and that’s why it took two years the last time. We have not decided to do it, but we keep on looking at each other and talking about it a little bit. ...
My bet is, they'll do another. And in less than three or four years.
Currently, Mr. Brooks seems to be having more success with animation than live-action. So he might have an incentive to move back to his strong suit sooner rather than later.