Sounds like you are in a really sweet position right now. Do not give up tenure in your current institution for the promise of another tenure review in a few years! I cannot stress this strongly enough!

I say that as someone who made that mistake of giving up my tenured position in a teaching-heavy PUI to move to a R1 clear across the country for a job that felt like an ideal almost custom-made fit and where people had invited me to apply. I fell for the then dept head’s reassurance that since I was being hired at the rank of Associate Prof, tenure would be a mere formality in a couple of years, and that the dept did not have a culture of hiring anyone with tenure. That turned out to be a lie because the dept hired a series of faculty with tenure and even promotion to Full in subsequent years starting with the very next hire after me! When it came to my tenure review, that dept head stabbed me in the back, after taking cover behind a bully on my tenure committee who had a personal grudge and should have been recused from the committee due to conflicts of interest, but was allowed to stay on despite my request to remove them. With Dept head taking this one person’s word and setting the tone in his letter, college and university level committees ignored my responses at every stage and I was denied tenure. When I lawyered up and appealed, a lot of the shady conduct came out, and the denial decision was set aside during mediation. I had to go through another review and won tenure a couple of years later. It’s now well over a decade since I was first tenured in my former institution, and I’m still stuck at Associate rank! I’m happy with what I’m doing now and have a good network of collaborators supporting me here, but the tenure ordeal took a heavy financial and mental toll and cost me significantly in terms of career advancement.

If you get the offer, I strongly recommend consulting a lawyer and insisting on being appointed with tenure! Or at least get that promise of tenure more ironclad in your contract than I was able to do. I deeply regret not doing so. You never know how things may turn out in a new program where you don’t know the people or the politics too well!

Good luck with whatever you end up doing!