I'm certain that, with regard to everyone's personal interests, with regard to everyone's personal capabilities, with regard to everyone's personal liabilities, if Russia attacks either Baltics or Ukraine, there will be no "WW3" and there will be no "Article 5" implementation, and I have been saying this for about close to a decade now. Nobody wants WW3, as there will be no winners in it. There is nothing of value to win from protecting proxy states at the threat of personal extermination.
The only, sole, reason, why NATO keeps promising that it will stay true to its "eastern commitments" is for the sake of protecting NATO's own reputation, which in turn protects its ability to continue its existence, which in turn protects its ability to play politics and circle-jerk on global decisions such as in the UN or UN Security Council, or in trade wars against "mutual" (not really) enemies. But all of this is soft politics. And soft politics go away when war begins, where survival becomes a number-one priority, and image/optics/reputation become of little interest to all participants.
The question however is whether Russia is at all interested in taking those territories by force. It seems to me that the long-term goal of big politics that are playing out today is the big new "silk road" initiative, with the global economic/political centers shifting eastwards. The collapse of US influence, and the crippling or potentially eventual collapse of NATO aren't life-changing or history-changing tragedies in themselves, and have no role in history in isolated manner. They're just few of the many chips that are falling into place, inevitably so, for the coming new "configuration" of the world and its economy.
Stuff like unions, alliances, treaties are just symptoms of a deeper but fundamentally natural global process which people are just adapting to, but not really driving themselves.