Even if Russia manages to hold on to Donbas and Lugansk, which is not a foregone conclusion by a long shot, it will be a pyrrhic victory that they will regret for a long, long time.
Of course it is not going to get limited to LDNR anymore. Nobody is going to let a hostile regime to stay on the Russian border anymore. And given the level of NATO involvement, it is going to be much more humiliating for NATO than Afghanistan.