Pretty mature technology. We've explored the various corners of the envelope and have sorted out what works well and durably, and with most positive mechanics/ergonomics ... and all the other variations of what works ok-ish, but less optimally. Top breaks, swap-cylinder reloads, odd loading systems (Trounds?), etc. All have their major purported "plus" that proves to be interesting but not nearly valuable enough to outweigh all the other "minuses" that come with it.
The newest real innovation is the Mateba/Rhino low-position firing orientation, but even that has proved to be nothing more than an academic exercise serving to prove out another evolutionary dead end. Reorganizing the structures of the revolver to accommodate sighting, firing, and handling the weapon with the barrel dropped low disrupted the optimal arrangement of the parts as developed so long ago -- hence the oddball firing grip and tortured trigger angle of the Rhino. Works fine, just doesn't do anything better, and some important things not as well.
Revolvers will continue to be very good at a specific niche of the shooting world. Able to fit and handle large, powerful cartridges (which autos can't because of the feeding through the grip). Able to handle wildly varying loads functionally. Able to attain high levels of accuracy with proper construction. And the trade-offs will continue to be relatively slow reloading and relatively large bulk for the payload carried.
Improvements will be almost entirely in the realm of "how" rather than "what." Machining is going to continue to get more accurate and cheaper. It won't be too many generations from now before it truly will be possible to build a Python-level gun right off the laser/edm/molecular-printing/whatever machine, or even something more perfect. The polymer stuff will continue to improve. Some tech advances in ammunition will probably come along, too. But I think that the revolvers of tomorrow are going to be pretty similar to those of today.
