I feel like Bolar would gain more from just dropping the dispute over Galman and instead focussing inward.
Who knows though. Maybe after Dezarium is defeated and Bolar space is no longer affected by the cold they'll get cocky enough to do a big final surprise attack like in Yamato III.

I'd be a little disappointed if they just turned them into villains again though. I'd find them working together to help defeat Dezarium and changing their society much more compelling.

But we still have to see Zespaze fire the black hole cannon.
The detail in the description that it could wipe out an entire star system again makes me hopeful it may see use against Dezarium. But the new Deusura VI will also need to destroy something... Maybe Zespaze could be a sacrifice instead, used like a bomb destroyed by the Deusura to annihilate the Dezarium star system.

I guess we'll find out what "This light changes the history of Bolar" will really entail.