I'd say each of Tomi, Logan, and Zion have a chance to make the rotation.
Tomi probably has the best chance of the three. My guess is Caitlin, Alexis, and Gabbie start at the beginning of the season. After them, Tomi, Kate, Lauren, Megan, and Zion will all battle for guard minutes. Tomi was ahead of Kate, Megan, and Zion last year. She's a good shooter, and is athletic enough to be a good defender. But her rotation place is hardly secure. I wouldn't be shocked to see one of those other three jump her, or see Lauren come in and contribute right away.
Zion is interesting, because she didn't play for much of last year. Then later in the year she started spelling Doyle at PG. Caitlin will probably play similar minutes as Doyle, so Zion could step back into that backup PG role this year. Alternatively, Gabbie or someone else could fill the backup PG role and push Zion out of the rotation again. I don't think Zion will make the rotation as an off-ball guard.
Logan is also interesting, because she played some minutes at the 5 last year, despite not really being a prototypical 5. This year, Monica and McKenna will be the starting 4 and 5. Sharon is the natural backup at the 5, and Kate the natural backup at the 4 in a smaller lineup. Logan's will need to beat out one of them to get into the rotation.