Well, Wily came up with Zero regardless of X. he made Zero to defeat Rock and Bass. But, as we know now, he was sealed away due to a cognitive flaw making him violent and disobedient. However, when Wily learned of X, he re purposed Zero to defeat X instead.
but if he never did that, what would he have done with him?
Also, I dunno, it seems like there are no classic style robots by the X series. Only one we've seen is Auto in an X3 PS cutscene.
I would imagine they would send the military after him. And eventually, the military would defeat him. but would he be defeated and then studied, possibly reprogrammed? or destroyed and then studied?
Certainly, a race of reploids made in Zero's image would be something interesting.