Peter Zeihan, who cut his professional teeth at Stratfor, now runs his own geopolitical shop - Zeihan on Geopolitics. His essay examines the implications of the death of NATO. Hat tip to RealClearWorld for the link.
Depending on your viewpoint, this is either a very interesting piece of speculative fiction or of forecasting. He doesn't quite convince me NATO is dead.
Zeihan apparently bases his conclusion on Trump's recent failure to mention Article 5 in his Brussels speech to NATO leadership. Article 5 states an attack on any member nation will be viewed as an attack on all members.
I've seen Trump change his mind often enough to be unsure this "failure" means anything at all. It can, or it may not ... there's no way to know a priori. Let's hope we never learn if Trump actually intended to slight Article 5.
Zeihan is certain Russia will attack NATO somewhere and he, at least, believes the U.S. will shrug off the attack, let it happen. Intriguingly, the author seems to picture a no-NATO future as liberating for U.S. foreign policy.
The essay is a great read; if NATO dies much of what Zeihan forecasts may happen. I suggest you read it that way, as an exploration of a future without NATO, rather than as a forecast of the actual most likely future.
My best guess as a non-expert: as long as Russia is a threat, NATO will struggle along. When Russia's 'slomo' demographic implosion finally removes it as a threat, NATO will wither.