I don't really see the analogy. MS bootstrapped fairly naturally (with the help of a great deal of luck along the way) from BASIC to progressively more sophisticated OSes, each of which closely followed well-established pre-existing models. AFAIK (I'm not an expert) there are no viable existing models out there for a big next step from the Boosted Board.

Even assuming infinite battery life, what's the form factor? A wheelchair won't cut it. A Segway-like thing won't cut it. A unicycle won't cut it. A conventional bicycle won't cut it. A recumbent bike or trike won't cut it. Roller-skates won't cut it. Exoskeletal legs won't cut it. Many of these things are of proven usefulness, but they've never been general-purpose substitutes or augmentors for pedestrianism. A version of some of the above which folds into something unprecedentedly small and light might begin to cut it, but how is that achievable within present-day engineering constraints?