all formats have their roles, killing any of them is not the answer imo. it is very tough to debut straight to test cricket, i know people say you can't select a player for one format based off results of another but a young up coming player can get exposure to quality bowling in the shorter formats before entering test cricket which is the toughest version of the sport. ODI cricket allows players, especially batsmen to work on their allround skills, as they learn when and how to accelerate and when not to, it can really help them understand how to play in different situations and conditions which i don't really think t20 cricket can help as much with.
t20 has it's place, it's a money maker, it's excitement but i think they need to limit how much is played so the format isn't overexposed. t20 is already getting less crowds than it was bringing in when it first came to internationals and it being played so much doesn't help, it also takes crowds away from the other formats. same goes with ODIs, they shouldn't play to many, not that long ago we were getting ODI series that were 5+ matches and that's to much imo.
All Time Test XI: 1 Hobbs 2 B.Richards 3 Bradman 4 Pollock 5 V.Richards 6 Sobers 7 Gilchrist 8 Procter 9 Miller 10 Marshall 11 Warne