TurboGears is built around a similar idea to what powers Linux and UNIX: Small tools, working together to make big jobs possible.
We scour the Python community, looking for the best tools out there. When we find them, we find ways to merge what they do into the TurboGears stack.
Because of this, we have used such tools as Kid, Genshi, Mako, SQLObject, and SQLAlchemy.
Each of those tools was the right choice to make at that time. As technology moves on, though, any of them can be displaced.
This is what happened with SQLObject vs SQLAlchemy. While SQLObject is fully supported in the 1.x series, SQLAlchemy has surpassed the capabilities of SQLObject in so many ways that SQLAlchemy was the only real choice for TurboGears 2.x.
We don’t know what tools will be the best tomorrow; we do know that when we find them, TurboGears will be able to support them.