I don't see any forcing, Mumbai is so multicultural, all type of people will flock to it. Targeting Shah Rukh Khan that he has not spoken in favor of Marathis (mixed bag with the IPL issue) is wrong.
Basic issue is large-scale demographic changes, which may have an impact on local cultures.
Personally, I enjoy the unique culture of each end every region, North to South, East to West.
If, for example, Kannada speaking people in Bangalore feel insecure (which they sometimes do), I tend to view that sympathetically - even if I were not from that region, I would be poorer without their culture and traditions.
I want each region to preserve its heritage - Bhangra from Punjab, Rabindra Sangeet from Bengal, the Onam festival from Kerela, the folk songs and dances of the tribals etc. That is an important part of what makes India what it is. Some people could not care less, but I don't side with such people.
The unity of the country has to go together with respect for local traditions. It should not be exclusively one or the other.
Perhaps one option would be to give voting rights in local elections to migrants only after they have been assimilated into the local ethos.
Ultimately this may be an uphill struggle. Who knows, in 100 years there will be only one language throughout the world and that would be English. Possibly Chinese and Japanese may survive in some weakened form but for South Asian languages the outlook is bleak.