Ah, my bad. I thought you already had it and tried to install but it didn't work.
Honestly, that's the best way to go to be sure and save a lot of potential trouble. Upgrading OS X over an existing install is generally not problematic, but that's not always true and I think most of us have learned that the hard way.
I think it's unlikely to work, but have at it. If it does work, then yay.
So their drivers for 10.10.x don't fix that? Well if you aren't looking for a solution, then that's cool, but I'd wager that the problem can be solved. Heck, I got my neighbor's all-in-one working after the manufacturer failed to provide driver updates for Yosemite. It was a simple Terminal command that "softened" the sandboxing restrictions on an existing driver. Or something to that effect. He was dumbstruck when I found and applied the fix in minutes.