Hi MasthaX,
there's nothing to stop you upgrading to 7.2, just read the release announcement http://forums.contribs.org/index.php?topic=37872.0 you will find upgrade instructions there.
7.2 does not upgrade PHP or MySQL to v5 however, and doing so manually isn't for the faint-hearted.
There are several forum threads on the subject of upgrading PHP & MySQL if you really want to go ahead with it though.
Nick
Well i couldn't find a good thread(only in French, and I'm not good at it!). Manually upgrading PHP is a little bit harder i guess because SME uses templates. But are there any good tutorials/threads?