I know several people already created TTF fonts, but I believe this goes slightly beyond.
This cart is a tool that vectorises the PICO-8 font and exports it to %APPDATA%/pico-8/carts/font.sfd.p8l . You can then open that file in FontForge and modify it to your will, then export it as TrueType, PostScript etc.
It should be fully forward-compatible and if Zep ever changes a glyph, then the resulting TTF file will change accordingly.
For instance, if you are lucky enough to have a PICO-8 Gold Account™ and the latest preview version with the chr() function and the kana glyphs you’ll even get Japanese support:
Here it is in action in the Windows font settings:
And here it is in a toy application: