evolution
The reason you don't see much "revolution' in wheelgun designs is because of EVOLUTION. The modern revolver is pretty much darn near perfect. Reliable, durable, accurate, superior to other guns in so many ways, why would it evolve? Take a long barrelled 629 and load it with 180 grain ammo. You have ballistics aproaching deer rifle status in a safer, faster and more versatile package.
Take the real needs of a basic self defense piece. Speed, power and accuracy. What is quicker into action and more final than a big bore snubby?
Firepower? When the high cap nines failed in Miami, Agent Morales ended the fight with a revolver and a shotgun.
Innovations that would make the revolver more technically complex would rob it of reliability. Therefore, as we have seen over the past couple of years the main changes have been metalurgical and in capacity. Thats about it. The modern revolver evolved over a century into the ultimate in dependable, safe, field proven life saving equipment.
Top breaks had one advantage only, simultaneious ejection. Trust me, had they been an improvement they, and not side ejectors would have been the mainstay for the past century. There is a very good reason that the basic design of the revolver has only changed cosmetically over the past 100 years. It didn't need to be improved.