And like others have said, Wizards really needs to nail down all of its online tools to be completely working and not merely in development before announcing 5E. For that tablet PCs need to be the popular standard. Android is already dominating the market much more than iPad is, but android still doesn't have that "if you want to make a program you make it for android" feel of it yet. Right now it still has the feel of, "I want an iPhone, but I don't want AT&T, so I guess I'll get Android," feel. Android is going to win, but it doesn't have the "go-to"-ness about it yet, much like Windows didn't have that go-to-ness about it until Win95 came along.
Truth be told, I wouldn't be surprised if 5E didn't have printed books. It makes total sense to go completely online and drop the cost of printing book completely (which is not insignificant). We're not at the point in our culture where ebooks are as readily accepted yet, but we will be. In about 3-5 years.
The sense I am getting from Wizards right now (and frankly, most of the industry) is we're in the later days of the print => electronic transition. Print is shrinking, but it ain't dead yet. The majority of the major company's profits are from print. But if everyone had a TabletPC, that would probably flip overnight. Wizards is probably planning to hold off on 5E until that becomes true. And frankly they should. It would be the perfect time to launch a new edition and if they have their electronic tools ready to go, they can reclaim their place as a major industry juggernaut. All it takes is timing, planning, coordination, and money.
We know Wizards has the money. I don't know enough about Wizards' internal working enough to even guess if they have the timing, planning or coordination thing down. I hope they do. It really would be nice to see Wizards lead the gaming industry charge into the electronic market in ways we have yet to see.