I was thinking of buying mi4 16 gb for my sis but when I read the reviews on flipkart, all the buyers (certified) are only saying one thing that the device overheats a lot even with minimal use!!

Anyone who bought mi4 facing this issue?
I am not sure now wether to buy it or not....

I think mi4 is not a proper upgrade from mi3...
Dude, you may be right about Mi4 not being a big update, but that's the culture nowadays, with mostly every company.
Regarding overheating, let me tell you that I have a Redmi 1S which I've posted a review of too, on this site.
Earlier it also used to overheat, but on software update v45, the issue is solved.
When a Rs. 6000 phone can get updates even today, I have all the reasons to believe Mi should solve your problem too by a software update. They might underclock the hardware slightly, or make some other adjustments to other internal conditions...
I would say, if you can wait, then wait. You'll know about the update status on internet. Otherwise, get it.
stay away from Xioami thats all.
Ouch! That's a kick to Mi's nuts.

Let's be positive... Surely, an update will roll out.