I may be able to get through this generation with 32 GB which has changed from a confident definitely before launch. Every retail game seems to require a patch right out of the box then subsequent patches. Additionally, I'm actually buying downloadable games. Trine 2 was almost 2 GB. I really want to support the indie game scene on Wii U since they're the third parties who damn about the console. If there's a retail version, I'll always get that. I currently have about 22 GB left after deleting Tank! Tank! Tank! which was awful.
I would have preferred a self-contained console with a hard drive bay, aesthetically and more importantly, for cat-proofing purposes (I am aware of the Y-cable solution). And isn't SATA faster than USB 2.0? I don't think I'd need much more than 32 GB if I ever went over so perhaps a thumb drive would suffice. Physically, they've become really small in size so I would probably forget it was even there.