Theyve been fighting for kills, not land, for the entire war. The point would be that eventually they can make many safe encirclements once the defenders are sufficiently thinned out.I wouldn't get too excited about any possible "cauldron." In this entire war, Russia has only managed one encirclement in Mariupol. And even then it took months to eliminate the defenders.
Best case scenario - Russia surrounds Avdeevka on three sides, Ukraine loses a lot of troops, and Ukraine finally withdraws.
More likely scenario - nothing exciting happens in Avdeevka for the next half year. I remember in August when the Russians looked threatening towards Kupyansk. Several months later, and looks like Kupyansk isn't going to fall anytime soon.
If Ukraine isn't able to make any plays and they just keep losing men and materiel, we're simply waiting for the transition point when manning the front isn't an option anymore.