They're there because of the failed coup attempt, there is no build up, it where they were exiled too.
Where they go from there is where the guess work comes in.
I would assume the Poles will be waiting for them even though there is not really much chance that they would be stupid enough to try and attack Poland, despite Lukashenko's bluster trying to impress Putin.
I would also assume there is a huge barrage of arty waiting for them if they step back into Ukraine.
These are or were highly paid mercs, with convicts mixed in, whos paying them those big wages now? With them being drafted into the Russian army I would assume the wages would be basic pay. Will they even want to fight for that?
There is a good chance those mercs stay put and and sit this out, doubtful but they just might say no. There boss was Prigozhin, they may demand his release if they are to fight again.