I had actually been wondering about this as I do think Kobo have shipped different "factory firmware" levels as time progressed.
The upgrade to 2.0.0 contains
Code:
Amasis
Avenir
georgia
GillSans
Gothic MB101.otf [only the one weight]
Rockwell
Ryumin.otf [only the one weight]
The two fonts in single weight are also the only ones in otf format; the rest are ttf's. The two of them are also far far larger in size; probably contain all characters.