IMO, likeliest thing, is that nobody will actually use nukes unless they are actually threatened - not just diplomatic semantic wrangling but really, actually threatened. With one exception: People who are seriously mentally abnormal. As much as we love to hate Putin, I don't think he's anywhere close to that category. North Korea, yes, maybe. Any country with Islamic principles as its motivation, makes it possible too.
Putin is just a normal dictator who, I believe, ultimately wants to live a "semi normal life". We shouldn't prance around declaring that out loud to him (because anyone is capable of losing their head), though. Which I'm sure Biden will do as soon as the thought occurs to him, because he is a moron who also announces in great detail which arms we are shipping to Ukraine so that Russia can be as prepared as possible.
He is not going to start nuking the world just because people joined NATO. They will all continue posturing and preening their feathers until time gives them little opportunities to slowly stand down from each other in various ways gradually.
Politics and power relationships are full of seeming ridiculous contradictions. Ponder the fact that Russia and China are even on the UN Security Council, I mean the whole thing is a laughable sham, but they get off on it and maybe it helps maintain some "balance of power", if only in their heads.
I believe at the end of the day this Putin thing is winding down and will go nowhere. He will annex that one little territory whose appearance of choice is being currently manipulated and that is about it.
Not to change the subject, but I think the bigger story of the decade(?) continues to be China. Russia needs attention right now, yes, but we must stay focused on the country which is actually racing ahead of us on EVERY.IMAGINABLE.FRONT. Ranging from technology to medicine to cyber-warfare to traditional military to dozens upon dozens upon dozens of interesting random things you've probably never heard of, such as they own the brand that hundreds of millions of women across the world including the US use for pregnancy testing to get complex and useful genetic information that nobody else has - I mean the list goes on and on.
We have to continue to focus on traditional Republican priorities: strong defense! which now includes high tech and traditional, a strong and muscular military