They would take away the selling point frlm their streaming service.
No way this will happen
Reposting something I've said before.
Using PSNow for PS2 or PSX games is not viable at all.
SD video can be around a GB/half a GB an hour. streaming more than a few hours will easily get into "more data than the game disk" territory.
That said, for any PS1 game, by the time you've played the game for an hour or two over streaming video, you've already used up enough bandwidth to download all the game data and store it locally. For most PS2 games, it would take longer, but usually not as long as it would take to finish the game.
So it may actually cost MORE money for Sony if they stream old PS1 / PS2 stuff on PS Now rather then utilize software based emulation.
I don't think Sony wants to foot the bill for their hosting costs to exceed that of bandwidth it would take just to download locally. They would make them lose money if they did that.
With the PS3 streaming there are varied prices per game (I'm sure they have a networking adviser giving the details to a bean counter to estimate usage costs to make it a profitable juncture) At least this is what makes the most sense.
Streaming old PS2 and PSOne titles however, doesn't seem realistic fit into this scope. (At least not in a way that doesn't cost Sony more money to stream rather then sell direct downloads)