I don’t think it’s a coincidence that the US announced it would lift the ban on American contractors going to Ukraine at the same time as this. Russia reaps what it sows. Ukraine gets highly payed and skilled contractors, in return, Russia gets malnourished and untrained Korean conscripts.
I doubt Bernie himself will but technically it’s not too late. The Democratic national convention hasn’t happened yet and after the debate there’s been a renewed push to pick someone else