I doubt it will ever work with SQLAlchemy, it comes with its own ORM layer. Does Django work with SQLAlchemy yet?
Yet, who determines what the best of breed is? How much time have you spent evaluated the web2py DAL vs SQLAlchemy to reach this conclusion? Or are you basing your judgement solely on the fact that SQLAlchemy has been out there longer and therefore it is more popular?
If you have pros/cons about web2py vs SQLAlchemy I would like to hear some concrete examples. They could help us improve it.