IMO, putting Rohit at 4 in T20's is not a very good idea. Him as opener is the best way to get some runs out of him. He's been most comfortable batting there and he's scored the bulk of his runs there. Putting him at 4 will make him fail. He doesn't rotate the strike a whole lot, which is crucial in the middle overs and he generally takes his time building dots. It would be different story in ODIs though. People keep referring back to when he batted in the middle order, but it's a serious shift if you haven't done so for India in a certain amount of years. Even after that knock yesterday, it puts him further back from batting in the middle order.
It looks like India will have to go with this setup. It's unfortunate having our best batsman at 4, where he isn't able to score a lot of runs. But with quality players knocking down the doors, it seems it will have to remain that way unless someone loses form, but it wouldn't happen until a couple of months later.
Dhawan shouldn't and won't be dropped. He was a valuable asset for SRH in this year's IPL, and after losing form in 2016-17, he's came back strong. He had some bizarre dismissals and some unlucky moments as well. It will take him about five more matches to be dropped if he doesn't score. This will keep Rahul at 3 for the next few T20 series.
Even though I am opposed to Rohit at 4 in T20's, it might be better to accommodate him at 4 in ODIs. He generally takes his time, and in ODI's time is not a massive issue as it is in T20, with conceding dots being crucial. If he bats at 4, he will come in mostly around the 20th over mark, giving him 30 overs to score. And he would bat well with either Rahul/Dhawan/Kohli who play briskly in the middle overs anyway, allowing Rohit to settle himself down before he is able to hit around the 40th over mark or even before. Rahul is in the form of his life. With that sort of confidence he can do wonders for India. Putting him at 4 wouldn't be a bad idea, as he could bat around 30 overs, but if he settles in opening he can make a huge score.