Mac Rumors and Daring Fireball point out Apple is explicitly stating they will not worry about supporting third party devices with future iTunes updates.
Apple is aware that some third-parties claim that their digital media players are able to sync with Apple software. However, Apple does not provide support for, or test for compatibility with, non-Apple digital media players and, because software changes over time, newer versions of Apple's iTunes software may no longer provide syncing functionality with non-Apple digital media players.
The "read between the lines" interpretation of the above goes something like this.
"Dear Pre Owners,
While you may be currently enjoying iTunes Sync with your shiny new Pre's (designed by former Apple employees), don't count on it for long."
I'm not sure Apple really is all that upset about this. The Pre doesn't sync very well with iTunes and the fact that it does at all could actually help shut down all of the complaints of an iTunes monopoly.
I think the Apple message could be taken at face value. It is not that Apple is going to actively try and cut the Pre out but Apple isn't going to waste any time making sure it works either. If future upgrades kill the Pre sync, then so be it. I've always felt that unless there is some agreement with Apple in place, Palm is foolish to tout this ability anyway. If Apple does break the sync, in the words of Ricky Ricardo, Palm is going to need to do a lot of 'splainin'.