Nah, all three formats can exists. Just a simple situation of smart scheduling in which 7 match and 5-match odi series are scrapped and at least 3 t20's are played over a series instead of many 1 off t20's which tends to threat the game as exhibition.
Every international series should then have a minimum of 3 tets, 3 odi's and 3 t20's and everything will be perfect. Only the Ashes, England vs S Africa and maybe aus vs ind and ind vs pakistan could have more tests because of the obvious historical significance of those series.
But again as most problems with world cricket, the problem horribly weak ICC is the reason why their is even a debate about this.
They have a corrupt board in the BCCI dictating things to them and they have implemented the IPL and along with cricket australia and the saffies board - created the champions league, which has clustered up the international calendar.
This disparity was horribly showed when the ICC announced its FTP scheduled for 2012 - 2020 in which the ipl was given an unofficial window and the champions league and official window. Madness.
ICC news: More Tests for major countries in FTP 2012-20 draft | Cricket News | Cricinfo ICC Site | ESPN Cricinfo
Test cricket is the pinnacle and t20's is third best format in terms of the standard of cricket although it is the cash cow that can potentially get more countries involved in the game.
Therefore the IPL needs to be revamped into a more international league and only when this happens should it get a window and the champions league should be scrapped.
Such an revamped IPL and the T20 international world-cup every two years, is all the t20 cricket we would need.
Test championship really isn't needed also and although the influence TV companies has on sports in general is fairly big, i for once agree with them for making the ICC scrap that idea for next year and bringing back the champions trophy.
All those weak idea's along all the constant changing of the rules in ODIs (they should have never moved away from the first15-overs restriction) because of some crazy belief that the middle-overs of odi's were too boring - is also another example of the poor administrative structure in the ICC.