So what happens when Ukraine loses? Are we at war with Russia then?

NATO can’t field an actual war against Russia, NATO countries don’t have the industrial capacity to do so. NATO has big scary tools, but not many of them, and in a protracted war where the industrial power wins Russia would win out. It would be very bloody, long, and NATO would lose, so it’s unlikely that there will be all-out war.

Russia has had its ass kicked with western hand-me-downs. Once they roll out the real kit, the whole thing will be over within days.