Anecdotally speaking, probably not. I haven't seen many poly relationships really last, nor have many of my friends (all queer).
I do see the rise of grandparents caring for children as a thing though, as wages continue to stagnate and both parents are forced to work. Intergenerational housing too. Multiple friends buying houses nearby and caring for kids if one parent is fiscally fortunate enough to be stay at home. That sort of thing.
I, after some admittedly short research found averages for monogamous relationships (including marriage) anywhere from 18 months to around 4 years. Which surprised the heck out of me. I've been Polyamorous for the last 24 years and the shortest relationship I've had in that time is 6 years. Most of my poly friends are also in quite long term relationships but that may just be a function of the friends I make.
This is also an entirely anecdotal response to your experiences as well.