All of your models will re-download as your app requests them.
Your app ships with a default set, and downloads optimal models for your loaded video at run time.
If you are concerned about losing the models we can take that into account, but we did not think people would be looking into their models folder and worrying about things like this.
There is an installer feature we are working that will let users keep their old models, but there are many things to consider with such a feature.
Backwards compatibility is not always possible and sometimes architecturally not worth the cost, so if we did for example create a new type of model, we would want a way to start with a fresh slate and not have any old files lying around.
Also, that is an extra 30GB you now have freed up that you can use for anything else. Of course over time your app will keep downloading models and the folder will get large again,
we are working on a solution to this for setting a size limit on the models folder but it is not out yet,
I hope that helps clarify and please let us know if there is anything else we can answer for you