Almost all of Indian male lineages(IE and Dravidian) now appear to be derived from Central Asia region. Michael Witzel, Indologist believes Dravidians moved from Central Asia region crossed Eastern Iran and reached southern IVC region(present day Sindh in Pakistan). It looks like genetic studies do support that theory as neither Arab nor Mediterranean lineages observed among Dravidians.
The article mentions a person named íu-iliSu, a translator from Meluhha. I just typed ilisu(iu ilisu did not return anything) and found villages with that names in Turkey and Azerbaijan, two Altaic countries. It's typical for Indians to keep village name as their second/first name. Probably, that person's name means íu from village iliSu(I am not sure about the sound changes as I can't pronounce that Altaic name).
Well, Michael Witzel believes IVC might have spoken an Austro-Asiatic language. But I wonder if it is possible for a civilized community to revert to tribalism. Is civilization just one way progress or can it go back to its tribalhood? If it was possible, what could be the reason? A loss of elite structure? Migration to places with remote chances of agriculture(IVC knew wheat cultivation)? How easy for an isolated tribe to come back to civilization? Would an occasional brilliant person from that tribe invest his/her time and energy in changing the whole tribe or would find it easier for him/her to merge with a civilized community by migrating. Will an isolated but close existence of a civilized community and a tribal community ensure a continued tribalhood(brain drain)? I am not sure, so I would rather think IVC must be either IE or Altaic.
Wheat and rice:
I don't think Dravidians of the past were either wheat or rice eaters. A big chunk of Karnataka and Andhra Pradesh still uses various millets for staple diet. Rice might have spread from North East region much later and as such did not reach North-West of South India.