An anonymous source told Develop today, there might be a chance the Wii U will support two tablets. Previously, Nintendo had claimed only one Tablet would be supported by the console and would not be sold separately. Rumor is Nintendo was afraid more than one tablet would scare off more casual gamers from multiplayer, but after all the questions they got about two touch screen controllers at E3, they decided to look into the issue further.
Develop's source also claims a few other pieces of the system's hardware haven't been set in stone yet. The amount of RAM and the processor speed have not been decided on yet. The source also says we will find the answers to all of these questions next E3, as the details of the hardware should be finalized by then.
The tablets themselves don't have heavy duty processors in them. All the imagery is streamed from the system. Hopefully this will keep the cost of the controller down if they do decide to sell it separately. Thinking about how much they charge for controllers now makes me weary of what one of those might cost with a touch screen on it.