Interesting that they're now opening this up, after flip-flopping a whole bunch. I haven't combed through all of the available API and support, but it could be interesting for indies. https://msdn.microsoft.com/en-us/windows/uwp/xbox-apps/devkit-activation
No, no it won't be. This is about on par with the XBLIG experience, but with less system access (devs can only access up to 1 GB of system RAM). The intent of this is to bring the UWP apps to the Xbox and try to merge the Windows 10-based platforms. It's also an easier way for them to ignore indie developers by "encouraging" them (read: pushing) to use this "open" platform instead of letting them in the real development program.
I haven't seen the API (and I don't care to because I won't do UWP development), but it is going to have whatever limitations that UWP apps do.
It's a neat idea, however, being UWP, it makes it almost useless to anyone who finds console development an attractive endeavour. XBLIG was a much better implementation of allowing anyone (who can pay the subscription fee) to develop games for a console without proving your developer credentials and shelling out for a development kit. Sure it was .NET CF but at least you could use XBL to a reasonable extent. This is more akin to buying another PC to develop your games on using a remote debugger.