These housing issues work out to nothing but simple arithmetic - if N people want to live in a region and you have K < N houses, N-K people are unhappy. Set K=N and all the problems are solved.
Anyway, it's the mutation of a city into another one, there are too many variables. Higher density sounds appealing but it may bring other problems, and the old residents end up displaced anyway. It's not going to be pretty, and the result is not going to be the San Francisco everyone loves, but well... it's not my city so why do I care.
Edit: quite a few edits
You are right that new Pune isn't the same Pune it used to be (or so I'm told) - now there are Gujus, Punjabis, Africans, white dudes and other non-Marathis there. As an American I'm a bit unsympathetic to "there goes the neighborhood".
Also, it's not about ethnic make up, it's about culture and identity. The neighborhood can go in a wildly different direction, and that's what people are lamenting, specially if it's culture-producing centers (let's admit it, the most that tech nerds produce are open source libraries for other tech nerds to consume). Anyway, urban centers come and go, SF's death will be a sad thing, but it happens all the time.
That largely depends on how quickly you want to build. Chinese companies can build whole skycrapers within weeks. http://www.theverge.com/2015/5/14/8608039/building-timelapse...