If Chris gives the rights to RCT 3DS there will be no problem for RCT4, Because Chris Sawyer is the one that decides whether it will make or not RCT4. The biggest problem was Chris Sawyer,but if I see that gives rights only need to expect of RCT4.RCT would require mega funding compared to the racing game, RCT as you know is a BIG popular game.
But I don't think Frontier / Atari did work well together, i think there were problems between the companies alot of the time.
I don't doubt (or at least i HOPE) RCT4 will be made, but it won't be by Frontier.
And i believe Chris Sawyer has given them the rights to do it other wise the 3DS version would not be in the making.
Also no one can predict the 3DS version will succeed, based on popular opinion (given nearly ALL RCT players prefer PC) i don't think it went down to well then it changed platform.
Atari wants to do RCT4 for this reason asked Ideas. The thing that Atari now has no money, and can not do RCT4. I would expect 4 or 5 years so if they will, really.
RCT 3DS will make profits, since many people have the Nintendo 3DS may buy it the game.