Yep, Putin will absolutely try to grab new land whenever he thinks he can get away with it, no matter how many young Russian men die in the process. To him it's just a game to fulfill his fantasies of being a great conquering czar, and for that reason credibility of NATO's article 5 is vital.

Even the good relations between EU and Russia pre-2014 were just theater on Russia's part. Here in Finland during those years shady Russian businessmen kept buying properties that made no financial sense, but were located close to critical infrastructure or military locations. They have never acted in good faith.