Girls that got their last 4* less than a month ago:
Sayo
Kaoru
Ako
Kokoro
Moca
Tsugu
Kanon
Misaki
Girls that got their last 4* 1-2 months ago:
Tsukushi
Rui
Arisa
Kasumi
Eve
Saaya
Girls that got their last 4* 2-3 months ago:
Chiyu
Rokka
Lisa
Rin Rin
Himari
Girls that got their last 4* 3-4 months ago:
Hina
Nanami
Maya
Tae
Yukinya
Aya
Chisato
Girls that got their last 4* 4-5 months ago:
Touko
Mashiro
Hagumi
Ran
Rimi
Girls that got their last 4* 5-6 months ago:
Tomoe
So our two options are a mixed event (since we haven't had much of those lately), or Pasupare (since they're the band with the least recent full-band event). I'm pretty sure this event will be mixed from seeing Popipa's cover of "Blue and Summer" (key word: summer), so Tomoe and Rimi as 4*s? Then I doubt it would be powerful, since Rimi's last 4 star was powerful.
Moving on to Pasupare. I don't think they will be in the next event since there's a chance the event will have the second set of summer lims, and Pasupare already had a lim summer set last year. If they WERE in the event, however, it HAS to be powerful (both bc we haven't a had powerful in a while and we need another power pasu event). I think we'd have an ayamaya or chisamaya pair, since ayachisa was used 3 times.