The good news is — if you don't want to upgrade to a Universal License — you don't have to.
Since you have an existing license, all updates are going to continue for the app as usual. You will receive regular update notifications with fixes and add-ons when released. Just as before.
The universal license version is marked as 4.x.x and may seem like a major version — but it's done this way to differentiate the builds for activation procedures.
Short answer — you are not stuck. Yes, you will receive updates.
And users with v4.x.x will receive the same updates except they will be for those who activated with their Universal License.