It's a matter of when, not if, and that _when_ was more than a decade ago. Round-up resistant Kochia (a weed) has spread across Western Canada and was first observed in 2011. Pretty difficult stuff to get out of your field once it takes root.

As for solutions, I agree with you that there's no single clean solution to mitigate resistance. But it seems like some weeds' reproduction paths are better suited for resistance than others (Kochia produces tens of thousands of seeds and spread similar to tumbleweeds, so there's a lot of potential for mixing and genetic diversity relative to other weeds).

https://saskpulse.com/resources/kochia-resistance-update-res...