I’ve thought about this before as well. As of how it is now, I believe 6061 and 7075 design have more or less reached its peak, at least in terms of a competitive standpoint. I feel like bimetal designs can still be improved a little in the future and maybe companies will start using new materials but as a whole, until something groundbreaking occurs, which may or may not happen in the next few years, we’ve nearly reached the peak of how well a yoyo can play.
I think we’ve been progressing nicely over the past 2 decades but things are definitely starting to slow down. we went from responsive>unresponsive that was huge. Then people started figuring out metal is better than plastic due to allowing for better weight distribution than plastic. While this was occurring people were starting to figure out what really makes a great yoyo(rim weight, low walls, H/V shape, etc). Then 7075 became a thing, and I the latest breakthrough was bimetal design which happened nearly 5 years ago. Not much has happened since then, some people have attempted using different rings other than steel for bimetals, trimetal design, etc, but none of those really showed a big impact in terms f performance.
Outside of traditional bimetals, some companies have tried to innovate with bitanium(luftverk most notably) and I think that’s our best bet at the next big step in terms of yoyo design and performance. I doubt it will catch on though since titanium is so expensive but who knows, over the past decade or two people have slowly been paying more and more for yoyos. Back in the days $50 was pretty much the cap for what any player will pay for a yoyo, then it jumped to $100 after aluminum designs became a thing, $150-$200 after 7075 became a thing, $200-$250 after bimetals, maybe people will start paying upwards of $300-$400 for bitanium yoyos in the near future.
However, this is just following yoyo design progression in terms of performance. Fun and enjoyment is a different thing and I still think there’s plenty of companies making great and unique designs out there not to mention budget metals and overall value for yoyos will slowly get better and better as the market becomes more flooded and competitive so these are all good signs.