Eh, I think a better analogy is trying to douse an inferno with an inferno. Tyranids gain biomass from this war, as well as newer and better ways to kill orks. Orks aren't advancing technologically to kill tyranids, but they would be getting a tougher hide, stronger bones, overall more resilient, as well as increasing in physical strength. Eventually one of them is going to lose, it's less a war of numbers and more a war of evolution. How far can both species go before they reach a biological plateau where they can just no longer advance. And we honestly can't say which would be the first to reach the plateau.
This is not about whether you personally like Oldcrons or Newcrons more, this is about who of the two would be more dangerous for the Nids. And to say it again, a unified force of Oldcrons would be infinitely more dangerous to the Tyranids than the eccentric saturday morning cartoon villains the Newcrons are.
You've also got a constant flow of Orks coming in from other areas because of the conflict. Kryptman probably regrets his decision of making these two fight.
Well, you also have a constant flow of Tyranids coming from the biomass, and probably any other Hive Fleets/Splinter Fleets that might show up. When this ends we'll either have a hell of a lot of tyranids, or orks with skin stronger than terminator armour who can bench press two dreadnoughts.
I wonder if orks would be able to use carnifexes and the like as the do squigoths. I mean when there is no more synapse.
A friend of a friend actually did a model about that. There was an ork riding on the back of a carnifex with a severed Guardsman's head hanging in front of it on a stick. Was beautiful.
oh god i just realized... remember that ork warboss that was able to lift the emperor up by his neck, and would have choked him out(AKA, squeezed his neck so tight that his bead popped off)if it weren't for horus saving him? yeah. i imagine those will be the warbosses we see if GW actually progresses octavius and isn't fucking stupid with some bullshit plot armor where ultramariens save the day there or something, taking on EVERY ORK FROM OCTAVIUS by themselves, at the loss of their first company.