If Pant regains his usual form and fitness then he would be the strongest contender for captaincy but only in Red ball cricket because for red ball you have to consider Home/Away conditions as well and he fits the bill for every condition. Rahul can challenge him in the test format if he starts working on his wicket-keeping, especially on turning wickets, plus agrees to bat in the middle order.
True. I feel that he would be a strong contender not just in tests, but in the T-20 format too. I see Pant, Rahul and Iyer being great potential contenders for captaincy in the future once Rohit steps down.
Hardik was pretty average as a captain so far which is why I feel that he should just focus on playing as an all-rounder which is what he does best.
At this very moment, i'd very much prefer role-based captaincy in every format so won't mind 3 different captains for all 3 formats. Virat and Rohit have already set the formula for ODI and Test formats. In this WC everyone had their set roles in every slot and it almost paid off. We already know what Virat's lead test team did in the last 6-7 years, results are there for everyone to see.
Pant's spot is not fixed in the T-20 Playing XI or in some cases squad. There is so much competition for middle-order (now top order too) WK batsman who can play the finisher role so IMO he's not a strong candidate in the T-20, and the same with the ODI format if KL and Kishan are in good nick.
KL could possibly fit the captaincy role in test and ODI if he gives up his dream of becoming an opener (That's where (Top-3) everyone wants to bat because it's glamorous and a marketable spot in terms of money and deals). He should bat in the middle order (similar to the last ODI WC) and must work on his Keeping. As far as T-20 goes, as an opening/middle order batter, his spot is also not secured in the playing XI. The point is for his survival he needs to become a WK batter. Also, he's too depressed to lead the team in T-20 (maybe ODI too), you need attacking cricket in a short format.
Pandaya actually did a satisfactory job in his T-20I captaincy gig, if he's fit then he should get a long rope. Shreyas has a perfect attitude for captaincy but his fitness is shaky due to back injuries so it's a tricky situation as you don't want your captain to break down in mid series.
Or maybe keep playing dumb charades in T-20 for a couple of months and when the WC comes, hand over the captaincy to Rohit, it won't be a bad idea as T-20 WC is around the corner.