We already know all the details on the HP TouchPad that will launch on July 1 if HP sticks to the launch date. You can bet that HP already has other TouchPad tablets in mind for the market, though the future devices might change based on how well received the first TouchPad is. I'm still not convinced that another major tablet OS will do well on the market with Android and iOS already available and garnering most of the developer support between them.
HP has filed for trademarks on the names of some of the future tablets that it might build. The six new names HP has filed a trademark for include TouchPadFlex, TouchPadPro, TouchPadTwin, TouchPadGeo, TouchPad7, and the TouchPadGo. What sort of hardware will go into those machines is anyone's guess and the names may never be used at all.
The TouchPad7 would presumably be a 7-inch version, though it could possibly be a tablet with Windows 7 too I guess. TouchPad Pro sounds like a good name for a tablet that packs a keyboard aimed at the professionals out there. TouchPadTwin sounds like a dual screen tablet to me and the TouchPadGo would be a decent name for a tablet with a smaller screen for more portability.