I'm not sure the back-playability (or whatever they call it) really matters that much.
Didn't we all rush out to buy DVD players when they first came out? I know when I did, they didn't give me 10 free movies!
After a while, you might go back to playing a VHS tape of a movie you don't have on DVD, but the difference in quality is remarkable & you're soon back to your DVD collection.
But, like VHS, you can still keep your PS2 & play those games on that console if you want to.
A little inconvenient, but if you're willing to pay to upgrade your hardware......