The problem was Microsoft replaced policies that indie developers perceived as bad and replaced them with policies that appear fair but actually are worse for the developers. XBLA definitely ghettoized indie games, but now they've got nearly no presence. Meanwhile releasing games on any day of the week might sound like a good thing, but in reality people want to go on and see what's new, and know when it's going to hit. (It's funny how we're going backwards on that point as downloadable games become more important, but there it is.) Meanwhile the parity clause isn't helping with mindshare.
Microsoft pioneered the space so they can certainly get back in the game, but I don't think they're all that interested in the idea, honestly.
The indie gap will never be closed. Sony has the most popular platform and unless something happens to substantially shift the market, it will stay that way.
I have to disagree with you there. The Vita's getting murdered by the 3DS in any category you can name and yet it's the much better indie platform. Part of that is Unity of course, but part of that is cultivation.