Nah. You can get a bamboo to a point where it is structurally sound in just a couple of months. Spent a few years in Japan and Thailand; they use it from everything from scaffolding to actual multi-level high-rise construction. They just process it by 'cooking' it in a low-temp oven for a while once it reaches the desired size. I don't know if they treat it with anything (I doubt it).

However, I think that even with a longer wait, you would wind up with a much more structurally sound bike frame. It wouldn't necessarily have to look like a typical bike frame... in fact, you could do some things with design by growing a shape that would be impossible to manufacture; especially when it comes to full suspension.