I'm actually in the same situation as you. Hopefully my iPad arrives tomorrow so I can have it while I watch the keynote. However I'm gonna wait to enable gestures until Steve confirms two things for me:
1. If IOS 5 will have the gestures.
2. When IOS 5 will be released.
If they are supposed to be included and IOS 5 is released relatively soon, then I'll wait till the update. Otherwise, if either of those two things aren't working out for me, I'm just gonna enable them and call it a day. So really it depends on what happens tomorrow.