It has been a month since Sony announced PS2 emulation on the PS4 which when I heard that,it is an interesting move for Sony to do.
PS2 games/classics emulated on PlayStation 4 is actually a good idea as it extends the amount of games you play on your console which really helps for those who want to go back or want to play it for the first time even though people give this feature a lot of backslash about it since you cannot use disc-base games which I understand that point.If you want to play disc-based PS2 games,play it on a PlayStation 2 or a Model 1 PS3 with PS2 compatibility.
It is basically the same with purchasing digital Xbox 360 games on Xbox One through XBLA alongside the same with digital Wii games on Wii U through the eShop alongside the Virtual Console games of NES,Super NES,Nintendo 64,GBA and DS.