Or will I have a lot of downloading to do after the upgrade?
TIA
No, they are frozen, and updates are obtained from the update repo.
Once in a blue moon, the volume of updates warrants a respin in between releases, but that’s pretty rare and almost like a new release.
You can install with “Net Install” CD, which only downloads packages you use, and ought to install the up to date versions from repositories.
Using a web proxy with a huge cache, the 2nd install, goes noticeably quicker than the first 