PS2 Emulation Now Possible on PS4 Follow

Unlikely. XI is kind of unique in that it required installation. And while it could be argued that data is data, the emulator would need to be further revised on how to interpret, store, and modify it. The linked article also mentions nothing about the efficacy of emulation across the thousands of games across the PS1/2 platforms. That's likely why it hasn't been made a bigger deal of yet. Anything short of 90-95% compatibility would probably get 'em slammed for touting the feature.

More to XI's point, however, they've made it sound like they code for PS2 first, then port to the others. They've commented on how PS2 devkits are rare and/or dying, and that's not changing with emulation.

They would have to move the actual development to the PC or PS3/PS4/Xbone to continue development, but it's highly unlikely due to their shining child FFXIV. Even DQX has slowed down in development while they focus on that one. So once the kits go kaput, that's basically it for XI unless SE wants to revive their original money printer.