Pulumi has two installable aspects. The API/SDK is the big bit, and it never needs to be switched: it's defined in your build environment.
The CLI is usually installed either globally or into ~/.pulumi, and theoretically may need to be switched, if your build practices require it. Generally, everything in the CLI is backwards compatible, so you should be able to avoid switching, but if your standards or processes require it, then you have a few options.