Haroon Lorgat says although the ICC World Twenty20 events are not too well spaced at the moment, it is only a matter of time and there was no danger for either the ODIs or the Tests.

The ICC chief executive stated this the 2010 ICC World Twenty20 was coming close on the heels of the 2009 edition and that this would be the third edition in four years. But that this would be rectified in future schedules.
Lorgat also stated he was aware of how close the 2010 IPL 3 and the 2010 ICC World Twenty20 in the Caribbean were, like the 2009 IPL 2 in South Africa and the 2009 ICC World Twenty20 in England. However, Lorgat chose to see only the positive side to it, at least when speaking to the media.
He felt that the IPL was becoming a bit of a worthy precursor to the mega ICC tournament and he felt it was a good thing as it whet the spectators' appetite for more. That is his (or the ICC's) perspective, at least for the time being.
He also stated that Test and ODIs faced no immediate threat from the Twenty20 version, citing the case of Sachin Tendulkar's ODI double century in Gwalior against South Africa.
2010 ICC World Twenty20: Preventing Another Caribbean Disaster, Says Haroon Lorgat
Afridi Moans Shortened Time between World Cups
Sachin Tendulkar's ODI Double Century Nails SA in ODI 2 at Half Time