The only reason that he's not making it (in my view) is because Dhoni is the skipper/ vice captain. He's afraid of competition, I know i'll get flamed for this but it's the truth. I have too seen him drop catches but i've seen him take some purely spectacular ones as well. he's a fantastic fielder and is probably on par if not better then Dhoni with the gloves. He's opening the batting and wicketkeeping which is essentially killing two birds with one stone, allowing Sanga's awesome brilliance with the bat when not donning the gloves.
Karthik is young and a fighter. If you look at how he played in England and South Africa you know how much of an awesome cricketer he can be. He had ONE bad series against Pakistan. He scored 97 in the tour match against whatever team we played in Australia and STILL got overlooked, even when the Dravid - Jaffer combo failed over and over and over and over again.