Can this emulator play PS1 games in the future?

Are you...implying that....it...might be possible? O_O

Not only implying, but confirming it.
DH added ARMv7 threading some time ago after we've all been discussing the projections of a Vita emulator and how it could be useful.
In fact, RPCS3 is already capable of loading Vita plain ELF files (unencrypted or debug, of course), but this is not a priority since more reverse engineering is needed.
Also, it will make more sense to write a standalone emulator first for the Vita and then explore these options later.