Wow ... it's like you don't believe any of this can be engineered ...
Battery ... I might have to give you that, but if a Mac laptop battery can be rated for 7 hours, how long would a battery last on a tablet that conceivably has no moving parts? Whatever the projection keyboard consumes, it could be earning right back.
Too little benefit ... Strongly disagree. A real keyboard, even a virtual one opens the tablet to nearly every market now served by a laptop.
Held in hand ... That's one way. Awkward? Heck no. People find flat surfaces for their laptops. They'll find one for their tablets too if it needs one.
No legs ... Why wouldn't a tablet have hinged legs so it can stand upright?
Table to tablet ... Maybe, why not a wireless mouse? Or even a virtual trackpad?
I'm not saying Apple WILL do any of this. But IF they did any of it, the whole idea of a laptop would seem so ... 20th century.
mt
Ok, wanna bet? (I am an engineer, btw. Not that it means anything, but it influences my opinion.).