Well may be i am misinterpreting the Asian pivot thing, i thought it was related to east Asia and pacific region rather than south Asia.
Secondly yes i do agree that we are seeing much better relations with US lately but would that stop Pakistan from offering Gawadar as a naval base to the Chinese, i believe no and with such kind of relations with China how can US trust Pakistan with its most sensitive stealth technology.
As for the room for Chinese expansion in Pakistan, well it depends more upon how quickly Chinese technology catch up with that of the US. If Chinese can offer Pakistan pretty much the same sophisticated weaponry that US has on offer then there is no chance that Pakistan will ever go for American weapons in the future. If there is some sanity left in our establishment then i believe they will never forget the 90's and presler.
My point is US can not offer us its top-notch technologies because of our closeness with China (we can't afford it either). And it can never curtail China's influence over Pakistan, in the coming decade or so we will get even closer with China.
US is moving its Atlantic fleet to Pacific, not Indian Ocean so i don't see us becoming a part of Asian pivot. But we can become part of their Anti-Isis alliance or anti-piracy fight e.t.c. That's what i believe but I might be wrong, please do correct me if that's the case.