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.

what do you mean with ARMv7 threading ?

This: https://github.com/DHrpcs3/rpcs3/commit/...1dc0a58e1a

DH set up a separate thread to run ELF files based on the ARM architecture (ARM v7 from the Cortex-A9 MPCore). In the commits afterwards there were some basic interpreter and disassembler implementations and finally the integration with the ELF loader.
While this is not really useful now, I believe the purpose would be to run Vita games in a parallel thread so later we could emulate the connectivity between PS3 and Vita games.