Tesla already does this to an extent with Autopilot/Full Self Driving, as well as rear heated seats on Model 3 Standard Range/SR+ and the Performance boost on Long Range. Although those are all currently flat upgrades, Musk confirmed that a FSD subscription will be available at some point. Premium Connectivity is also a subscription offering, giving access to some map upgrades and streaming media.

There's actually quite a few things that are software-locked on the Standard Range line with no upgrade path. The footwell lights, for instance, as well as fog lights on early models (current ones don't have them installed anymore).