Of this there is no doubt. They are meat for the grinder. There will be no good outcome for those put on the front line.
Dunno if they will be going front line though mate, about 3/4s of the Russian proper military force involved in the SMO isn't in the front line (think around 60k are currently) but having to do all the massive number of other roles required - my educated guess is once the 300k arrive it'll 'free up' the proper equipped and trained units to be committed to the combat zone.
Combined with a change in approach meaning Russia follows it's full doctrine of engagements without restraints which the SMO applies currently, then this could get very brutal very fast.
Seen reports that Russia have amassed between 700-900 combat aircraft close to Ukraine, up to now the air power has never been used on mass, 1-2 planes used in an area at a time etc, I think that we could see that approach changed soon.
Seen comments about how ineffective the Russian air force has been thus far, but they've never used it on mass (say like we saw the US do in Iraq first time round) we've also not seen them launch any strikes on government command centres, transport systems or the power, communications grid. (Isolated strike but no mass targetting with their best weapons) a change from SMO to war alters strategy hugely.
There's a reason hard liners like Kadyrov have for months been begging the Kremlin to let them off the leash because right now the military hasn't been operating whatsoever to prescribed doctrine - which few western sources have actually highlighted at all.