Litigation with company a can be delayed due to an IPR institution achieved by company b. So IPR institution could potentially put everything on hold for another 12+ months. I own another ticker that is going through this exact situation right now. All infringement suit dates got pushed back where they start again around when the IPR final written decision is due.
The other “uninvolved in the IPR” infringers may be waiting to talk about a settlement until they see no IPR institution. Else they potentially have 12+ months to push this off.