I have very low expectation for GTA: Chinatown Wars too. First off, anyone expecting anything remotely close to the PSP games will be terribly disappointed. This is a radically different GTA.
I don't think it will sell on Brand alone being so different from the games that made GTA what it is. It was pretty much have to find a new audience to introduce to GTA which in the crowded DS market can be hard.
Should sell decent but not amazing numbers.