The way I see it, Microsoft wants Xbox to be the home of Grand Theft Auto. They want people to think, "Oh, GTA? That Xbox game?" That's why they're going out of their way for the downloadable content and what not, so I think they'd be willing to spend some big cash to get everything Sony gets and more. I'd expect those three games to be Xbox Originals as well.
I would doubt it too. What might be more likely is GTA3/VC/SA to become available to download on Xbox Originals.
How could they be considered XBox originals if they were never originally on the XBox??? If they came to the Market Place or whatever on XBox Live! then they still couldn't be considered XBox originals because it didn't go to the XBox until 10 years or so after they were originally released.
I think Sony payed Rockstar money to have Grand Theft Auto on the PSOne so I think they're partially owned by Sony, in a way, not really though. The originals are basically Sony's territory.