I suppose Kellhus would have gotten the Gnosis at some point, yeah, but probably not until after the battle. And at that point, I'm not so sure the Inrithi would have won. Were they on the trajectory of victory before Kell showed up? I thought he kind of saved the day. What would he have done if he had to run all those miles back and found his host in shambles... I guess then Maithanet would have eventually showed up with all the Mandati in tow, but that would have looked kind of bad for the Thousand Temples, relying on the Mandate to win their Holy War.