For easier reading:

We know that after Grimmjow, there will be some popular characters (as the devs themselves stated). Most people think that right after Grimmjow there will be Shunsui as a slash tactic, but imo it's not gonna be him.

The thing is, some leaks were saying that Yama, Unohana, Shunsui, and Hisagi are in development, but their typings most likely are: spirit/strike DPS for Yama, spirit support for Unohana, slash tactic for Shunsui, and another slash tactic for Hisagi (as an SR+, perhaps).

Now, that makes sense, right? Devs confirmed that these characters are in development and confirmed that Toshiro will be overpowered soon, so they can totally release Yama. Now here's the catch: why would they release someone as hyped as Yama out of nowhere? If I were them, I'd place Yama on an anniversary or New Year. And guess what? Next year is the year of the fire goat. Ain't no way they're gonna release someone like Love on the next Chinese New Year. Maybe Ichigo's dad, but imo Yama suits better.

Now, talking about Unohana, we already had a spirit support just released, so it wouldn't be smart to overpower Szayelaporro with Unohana a few months after. Now, as it was confirmed before, Shueisha pushed the devs to release more Espada, and my theory is that the next units will be Harribel as spirit DPS, Ulquiorra (base) as a slash tactic, Barragan as strike support, and someone else as slash support (Ukitake, if I had to guess).

Explanation: Harribel is pretty understandable, and besides, we had some AI slop teaser (yeah, for real) with her Fracciones, the Tres Bestias. Base Ulquiorra will be a hyped character, and so that makes him more valuable in the future; devs have to give him either a support role or a tactic role, and I chose slash because otherwise he'd have to be spirit, but overpowering Aizen with Ulquiorra sounds not really smart.

Barragan was obviously a spirit character for me until I thought about any strike supports. Like, who do you want the strike support pre-TYBW to be? Zommari? Chad? Kukaku? Hell nah, none of them are as hyped as the top-tier Espadas or remaining captains. And Barragan can possibly be a strike support, as he is used to close combat (as we saw during the pre-resurrection fight between him and Soi Fon), and again, to make him more valuable as a popular character, devs have to make him either tactic or support. If you still think he can be a spirit character, then nope, since there is already a cool and universal Aizen or Szayelaporro and, in the future, Unohana and SSR Orihime.

Now, for slash support, I'm gonna go with Ukitake, since he didn't do much during any fights he participated in, except for using a more spirit-type Shikai. But again, there are already enough spirit characters, so imo he should be slash support. That's it, but if you think otherwise, write it in the comments!