You make it sound like Microsoft only has one customer and that customer wants XP support as a backend to Visual Studio. That's not true. Microsoft has bajillions of customers for Visual Studio. All of them want a CRT that is faster, safer and cheaper. Not all of them want XP support as a backend.
With XP having a market share of 38%-48% *) I think it's fair to expect that most customers are still interested in XP support.
*) Source: Various random reports found via https://www.google.com/#q=xp+market+share+2012