Well, he was a 4th round pick...so he probably wasn't on their minds as an "answer" at RB when they drafted him, but he is surely making a decent name for himself. He is a huge guy, so that would probably be a negative for him. But, there have been guys like him that have had very good NFL careers at starting RB. Eddie George is the obvious example.
Tiki is 30 right now, so he's probably got 3-4 more good years left. Jacobs could conceivably step in (or phase him out) in the coming years and get a lot of seasoning before then.
However, the problem I would see the Giants having is that they see Jacobs in this role so much this year that he never gets a chance to advance. They could use a 1st/2nd rounder on another RB in a few years and go from there.
Based on all of this, there's probably a decent chance that Jacobs becomes a T.J. Duckett clone down the line.