[asid61]

The problem with mecanum IMO is that they are basically the end. Apart from octacanum drives, mecanums don't have many places to go to design-wise. I think they will remain the same for a long time.

Swerve and tank drives, on the other hand, have a room for improvement. 221's Revolution Swerve weighs only a couple pounds per wheel, and their in-wheel Wild Swerve is fantastic. However, I still think that there is room for improvement- nobody's just found it yet.
Tank drives have changed little over the past few years, but gearboxes get more interesting every year.