I doubt Ronda Rousey will ever fight MMA again... first because her ego couldn't handle the "risk" of another devastating loss... second because (financially) it doesn't make much sense for her. There's no great demand to see her - which would be the only way some promoter would give her a big enough guarantee to make her want to take that risk.
Besides, she still has name recognition and can (almost certainly) earn as much in a year as a B-movie actress (doing horror or exploitation films) perhaps finding a movie franchise where she could play Jennifer Lawrence's "mean older sister" or "the evil cyborg" in a Lawrence helmed "Terminatix" film.
There's been talk of her appearing in WWE which would seem a no-brainer unless talk of her "knees being shot" is anywhere close to the mark. If so, that may not be practical. Many wrestlers I've heard, or read, about seem to have knee problems after doing 200+ "shows" per year.
All that said, I'd hate to see her (at age 30-ish) simply disappear....or worse. She's a personality and seems to know how to present herself on camera, which makes some kind of show business career a natural fit. Perhaps as a wrestling/MMA color commentator or a WWE "personality" as a promoter/manager of female fighters. It would give her face time and keep her name in front of the public while not subjecting her body to the rigors of 4-5 night a week stresses.