I would be very surprised if the Time War were ever re-visited. That was RTD's story, and with him gone, there's nothing else to do with the Time War. Note that since Moffat took over, there have only been two rather vague mentions of the Time War.
I would rather not see it unless we had a big budget for it. And I wouldn't want Moffat handling it anyway.
Which is a shame, since my favorite multi-Doctor story in my head features a brief but hilarious encounter between the 9th & 11th Doctors. Overall, it would involve multiple teams of Doctors roving around a maze (possibly within the TARDIS itself), trying to [science] the [science]. Some Doctors would work with each other. Others would set off on their own. Some Doctors would have a major role. Others would just be a brief cameo. Still others wouldn't be seen at all, just spoken of. I suddenly got this idea that no one else would want to work with the 7th Doctor because they're afraid of being sucked into one of his masterplans. 11th Doctor: "Oh no, no, no! Don't listen to him! He's scheming. He's got his scheming face on. I can see it. See, he's even got his scheming jumper on. Have you looked at yourself? All those question marks? Have you ever heard of trying too hard?" BTW, there's this fanfilm online called "How to Stop a Time Lord." It's a surprisingly good 10th/11th team-up. I mean, don't get me wrong, it is a fanfilm. The production values and acting leave something to be desired. (English does not seem to be the first language for any of the actors.) But it does a very good job of capturing the madcap tone of the series with all of the fast talking & running down corridors. The interaction between the 2 Doctors feels authentic and very funny and you see enough glimmers of promise that I'd like to see a professional remake with Tennant & Smith. Although, even with the amateur level of fanfilm acting here, the guy playing the 10th Doctor has captured enough of Tennant's mannerisms (and looks a lot like him if you don't get a good look) that it often feels like he's captured about 70% of the real thing. http://silverwolfpet.com/doctor-who-fan-film-how-to-stop-a-timelord/ Agreed. It could be particularly interesting if it mostly involved the companions who weren't left behind on present day Earth, like Susan, Steven, Jamie, Zoe, Romana, Nyssa, Turlough, and possibly Ace. I mean, it would be so easy to bring Zoe back on an otherwise unrelated space station/research outpost under siege story.
And there's certainly photographic proof from a stage play that "Ten-inch" is a considerable misnomer!
I hope they do a multi-Doctor story, and I hope they do it as a comedy. No Time War, no Omega, no villain who threatens to destroy the universe. That kind of thing can only work if it's done with tongue firmly planted in cheek.
That never stopped McKellen... Whom Patrick Stewart described (when sharing a dressing room) as "intimidating"!
Both Colin Baker and Peter Davison have said they don't think it's likely to happen. Colin Baker also said he was "neither for nor against" the idea: Which isn't quite "not interested," but also isn't terribly enthusiastic, especially about doing it merely to push fan nostalgia buttons.
Rather than a multi-doctor story, for the 50th anniversary maybe they should just have the story of how a younger first doctor left gallify etc..