You'll definitely not lose your data, no. If you get unlimited storage through your university, you will lose access to that and thus the ability to sync attached files > 300MB and access them across devices and through the web library. In that case, you can either buy storage or do without file sync. The files will remain on your local devices.
If you don't get storage through your school, changing the primary email address has no effect on your data at all.
If you get storage because of a university email address, you can keep that email address as a backup on your Zotero account and you'll still qualify for unlimited storage.
Upgrade Storage
If you get unlimited storage through your university, you will lose access to that and thus the ability to sync attached files > 300MB and access them across devices and through the web library. In that case, you can either buy storage or do without file sync. The files will remain on your local devices.
If you don't get storage through your school, changing the primary email address has no effect on your data at all.