I sorta feel Kohli is our best bet for No. 4 in the WC. A gun player like Kohli, who can effortlessly shift gears and the kind of ease with which he does it, HE SHOULD TAKE UP that pivotal spot. What that will do is is a few things
1) Move Rayudu up to No. 3 (or let Rahul play at 3). If its Rayudu it allows him a little more extra time to get himself in and then he expresses himself. If its Rahul, he fits in there and causes havoc if he gets going
2) If its Rayudu, it creates space between him and Dhoni. This is important, because we do not want them batting together for most of the time. If both are relatively new to the crease, our scoring rate will just nose dive spectacularly. If it's Rahul, it's even less of a worry.
I think Rahul is destined to be picked as the backup opener for the WC (I did have reservations over him yes, but I'd rather pick Rahul over Pant; India can take only two wicketkeepers to the WC squad and Pant has to fight it out with DK for that 2nd keeper spot). Both Rahul and Rayudu have to fight out for the No. 3 spot. Kohli takes No. 4 and then the finishers (Dhoni, Jadhav, Hardik) follow.