I think it will be a stalemate for a long time. I don't see any viable weapon that could be given to Ukraine to really allow them to make a push. It's really, really hard to advance against a combination of minefields, artillery and infantry with ATGMs waiting in trenches. Even if Ukraine is able to neutralize the helicopters and planes.
That's exactly the same problem that Russia had, Ukrainian artillery was able to wreck havoc on the Russian columns. Russia couldn't disperse their troops because of minefields. The surviving armor was picked apart by ATGMs and Ukrainian tanks.
Russia will most likely not collapse at this rate, either. They are able to manufacture a decent amount of hardware and ammo, so they will always have some. Some estimate Russia pumps out 250 tanks a year. Not much, not enough to replenish the 1500+ they lost, they will not be able to mount another big offensive, but it's still a decent number to keep up a static line.
The attrition could last forever as neither country is able to destroy or capture the factories that make the materiel.
