if they only port GTA III, VC and SA to the 3DS with 3D Id be very happy.

The GBA got a GTA title.  It bombed hard.  The DS got a GTA title that did fairly well given the demographics and structural changes to the game mechanics and deisgn.  The PSP version did much worse.   Saints Row, Metal Gear Solid, Resident Evil, Dead Or Alive and many otehr mature rated titles are already in development for the 3DS.  So say with any certainty that a GTA title will not appear on the 3DS is to ignore much that supports the notion that a GTA title will appear on the 3DS.

I think it's very likely, but I wouldn't say a 'given'

They're making one right now.

I am confident.

Of course it is. Can you name currently existing platform that has no GTA game ?

Ouch my bad. I was thinking they already have spin-off everywhere.

I think that the 3DS will be the PS2 of the next generation in handhelds. The DS did what the PS did, open up a new demographic, started slowly then exploded, sustained great sales, and gained the attention of 3rd party developers. 

The 3DS will do what the PS2 did, garner most of the exclusives of 3rd parties(like we're seeing), and continue what the DS has been doing. I really think the 3DS's first 2 years will even be bigger than the Wii's. So if GTA miss out on the 3DS, it's there loss, but from what im seeing, the 3DS is gonna be the console everyone wants just like the PS2 was. I really can't wait for this, i just recently bought a preowned DS for pokemon HG/SS and B/W, but the 3DS is in a whole different league apparently

If Grand Theft Auto: Chinatown Wars shouldn't have been released on NDS but on PSP as a exclusive game we can also safely say that Metal Gear Solid: Peace Walker should have been a NDS title because it was a huge flop.

There's much bigger enemy for 3DS than PS2 had ;) Iphone and other smartphones might steal the casual market with their simple extremly accessible and dirt cheap games on a medium you always carry around with yourself.

But then 3DS won't have any of the things which make hardcore despise wii. The planned library of games has some extremly good positions, it has buttons :), and it offers resonably good visual levels together with 3d screen so in early years it should sell amazingly to early adopters.