Smale's proof for d>=5 was unified. The d=4 and d=3 cases were special and those are special dimensions for a lot of reasons. "Low-dimensional topology", i.e. d=3 or d=4, is a big subject in its own right, because of those issues. At least for now, the prospect of unifying them with higher dimensions is somewhat remote. Basically in higher dimensions, there is more space to maneuver and things don't get in each other's way as much, so many proofs become easier. As well, many things are true in high dimensions and false in low dimensions, in which case unification is obviously impossible.. See also "curse of dimensionality" about why things are different for high dimensions.