It is transferable-yes, you will get issues if you take prompts and workflows tuned for one model and send them to another unchanged. But, most of the time, fixing it is just tinkering with some prompt templates
People port solutions between models all the time. It takes some work, but the amount of work involved is tractable
Plus: this is absolutely the kind of task a coding agent can accelerate
The biggest risk is if your solution is at the frontier of capability, and a competing model (even another frontier model) just can’t do it. But a lot of use cases, that isn’t the case. And even if that is the case today, decent odds in a few more months it won’t be
This is why there are a ton of corps running the open source models in house... Known costs, known performance, upgrade as you see fit. The consumer backlash against 4o was noted by a few orgs, and they saw the writing on the wall... they didnt want to develop against a platform built on quicksand (see openweb, apps on Facebook and a host of other examples).
There are people out there making smart AI business decisions, to have control over performance and costs.