So are any tablet computers able to interface with an Arduino

retrolefty:
Just wondering what might be available in the tablet world that might be able to communicate directly with an arduino via a USB cable?

And I assume there in not and not likely ever will be a tablet that will be able to run the arduino IDE directly? I guess a netbook would be the most likely candidate for a small portable arduino support platform?

Windows tablets have been around for about ten years now. I don't know if any of them qualify as tablets to you.
You could probably find both used or new Table PCs running Windows XP tablet PC edition, Windows Vista or Windows 7.
These should all be able to run the IDE just fine. Besides that, I doubt that they will be much fun.