Looks unlikely.If Saburo lives forever, he will desescalate (for a year,a century?) as implied on his TV speech("what is perfect doesn´t need a change") now being practically immortal doesn´t seem to have a reason for a direct confrontation; even if you end up without helping Hanako/Saburo (Yorinobu kills Hanako,takes control) you caused massive economic loss to Arasaka and Yorinobu retreats to Japan to cut losses (kind of the end of 4th Coporate War). Plus Militech is still pretty much under NUSA control, that was the problem that Arasaka face in 4th Corpo War.
On the other hand, Mike Pondsmith likes to reset his universe periodically so some kind of event could happen (please, don´t destroy Night City again CDPR, I have my Night City guide from CP2020 that I cannot use due to reurbanization...) that balance power... From shards, I would say that a NUSA vs Free States or NC free city seems more likely (there is a shard that pointed even a probability of that happening); this can trigger a Arasaka vs Militech turf in NC again since Arasaka supported NC against NUSA in the past you already have NUSA patronized gang in the game, 6th street and Araska patronized ones... so it might be a turf war and not a full war at the end.
PS: in other words,I think you already played a role in 5th corpo war but the game doesn't tell it to you explicitely
