This has been a big question i keep coming back to. It's very under stated just how good their in house emulator is. It was able to push almost perfect compatibility on a PSP. It has been ported to the PS3, and the ARM based PSV, which makes it hard to understand why they couldn't port it to another ARM based chipset. The only reason I can figure is that it has always been baked into their firmwares, and they didn't want to invest too much R&D on a nostalgia device that would have enough security to keep their emulator locked down.
I'm at least a little hopeful that it means they value the in house emulator enough not to let it get leaked, and maybe it'll see a return in PS5.
I suppose that is a possibility. I do think they are going to focus a lot more on B/C next gen given some of the statements and patents we have seen. Though, really, there is also no reason the PS4 doesn't at least play PS1 Classics from the store. Not sure why they have ignored that extra stream of revenue.