It's your call. If you are a hobbyist. I clearly understand. If you run a business where you have much more overhead than $200, then you are keeping a rusty link in your workflow.
Adobe should theoretically do as you suggest, but I find over the years, I'm not privy to the reasons, so can't say why.
CS5 is no longer sold or supported and an OS upgrade could damage it as Mac OS 10.10.1 did to CS5 Mac.
You do have time right now to decide if in the long run you want it or not. I'm a forum volunteer as is station_two, so we have nothing invested in our advice.
Gene
