If we want to pick nits, NS had a second source: TI. But that was, afaik, just paperwork at that point (and I honestly don't know if TI ever produced a 32k processor). It takes time to bring a second source on-line. And given the trouble NS had building the chips themselves, if I was IBM, I'd have Questions.
That said...even if NS could wave a magic wand and produce a second source, there were plenty of other reasons to discount the 32k, and I've never seen the slightest evidence that IBM ever considered it.
Fair enough. I still like to dream about alternative realities.
Dream away. How much weirder a dream would it be if IBM had gone Zilog? Fanbois endlessly arguing the superiority of segmented over paged memory? Terrible marketing from an oil company? Wordstar still the standard? I sorta like that multiverse option.