Rayman and mortal kombat are far from graphically intense games on console.
And no, the Vita won't get GTA V. Not only can the Vita probably not handle it, the Vita is limited in game size to 4gb or less, and I guarantee you GTA V well be like, 10GB on ps3
With Gaikai GTA V could very well one day be played on the Vita, yea that is looking far ahead or who knows maybe it isn't that far away..
I think the Vita can handle a smaller version or spin off of GTA V either way just like the ones that PSP had which honestly playing open world games on PSP was impressive enough and the VIta is a lot more powerful. Of course it won't look as pretty as the PC or console version of GTA V but it still should look great.
Only time will tell I suppose.
Their idea is that if they made a GTA for Vita, as long as it looked "decent", people will buy it anyway, just because it's GTA. While that might not necessarily mean any game made will be bad, it will probably mean it won't be as good as it could be