Beware of unmarked spoilers.
Yoruichi will use her cat form to help the PMMM girls.
Specifically, Yoruichi will present herself to Madoka and Sayaka, maybe even Mami and Kyoko, as a faithful version of the Mentor Mascot that Kyubey inverts, in order to turn them away from the incubator and convince them of the real situation.- This could, of course, have repercussions if the girls themselves find out that Yoruichi isn't who she says she is, should she go this route. Perhaps leading to a timeline reset.
Homura will get adopted into the Kurosaki family by the end
- Confirmed(?) Though it has not been made official, it has been stated multiple times by multiple members of the Kurosaki family that they consider Homura to be their sister/daughter.
Yhwach is the master of the Incubators
The two have fairly similar goals: Creating a world without death and staving off entropy, to the point where the two would align fairly well, and Chapter 77 has Kyubey reveal in an internal thought process to have a master. Said master could very well be Yhwach, who Yamamoto seems to have actually defeated in the past...and yet is still causing Soul Society trouble. Toshiro will die in the N + 1 timeline.
Or something else horrible will happen specifically to him (because this is PMMM and characters suffering horribly is a given). Toshiro has been focused on a lot this timeline and Kyubey sees him as a major threat and obstacle. Sayaka nearly contracted to save his life because of Kyubey's manipulations. Toshiro's death, injury, or worse will have major effects on the PMMM girls and his Bleach allies - especially Mami and maybe Homura, who he is close to in this timeline.There will be an eventual Arrancar equivalent of Witches.
Witches are already compared to being Hollows, with the Walpurgisnacht pretty much being at least a Gillian form of a Menos. Magica Record additionally brings up Doppels, which is the equivalent of Vizards (Shinigami/Puella Magi gaining Hollow/Witch powers). While human forms of Witches are partly touched up on (I.e., Candeloro, Giovanna, possibly Kazumi, and Homulily), we have yet to see them being a thing.- It might also be possible that a pregnant woman surviving a Witch attack results in the child being some variant type of Fullbringer. Though the Incubator would likely consider such children to be "waste products" of its system, and try to "recycle" the female ones and "dispose of" the male ones.
Sayaka and/or Madoka will end up becoming Substitute Shinigami in at least one timeline to prevent the Incubator from contracting them.
Heck, they might try stabbing a Zanpakuto into a Soul Gem to see if a Shinigami/Magical Girl hybrid pops out. Not with Homura, they won't risk losing their reset button that way, but Mami or Kyoko might volunteer for it.