I think an Indian business would much rather sway with a "dot com", or a "dot in" - Period. I don't really see that changing for the foreseeable future, as least in my view, given the way people think. I see these "dot com dot in" type domains to be fakes of the real "dot com", and no business wants that image. IMO
Is there a .com.in extension? Guess it was a typical error in some marketplace for the .co.in domain.
If it really exist, can anyone post which registrar supports it?