Do you really think WebOS will gain any traction under HP? HP is very deeply in bed with Microsoft, and I don't see that changing. HP bought Palm to send a message to Microsoft about how they were screwed over by Microsoft waffling around with Windows 7 Mobile. But, honestly, I don't see HP putting the commitment and push behind WebOS to make it work any better.
Personally, I'd wager that in a year or two the market will be iOS, Android, and "scraps" which'll mostly consist of the corporate users who are still waiting in line for their upgrades from Blackberries to iOS or Android.