It's not like maximum penalties are really given very often in cases like this, and certainly not for someone like DSK. His lawyers will get him a relatively good sentence even if he's guilty.
On another issue....I'm really having trouble figuring out what I personally believe. It would be nice if this were some big misunderstanding, but I dunno...
From what I read 20 years is likely to be the max punishment and even that is not particularly likely.
And so far there seems to be plenty of indications that he's guilty, while there is really nothing indicating that this is a conspiracy (which seems to be the only alternative explanation).
Anyway, since the police apparently have blood found on the sheets and semen found on the floor (that is, according to the media reports I've seen) I assume the case will be pretty clear-cut once the tests have been run.