NOTE - Title should be changed to something more into what am asking...
There are 2 cases I have seen when upgrading someone from the previous version of Ubuntu to the latest.
When the user has not even done an update for a while so now he/she has the updates for that version of Ubuntu and also the Distribution upgrade pending.
The user is up to date with all the updates for that particular version of Ubuntu and only needs to upgrade to the new distribution version.
I always recommend updating every package and THEN upgrading to the new distribution (Just in case, maybe it's me but I feel safer this way. It is more logical I guess). But what would happened or if it possible to upgrade to the latest distribution without first updating the packages for the version of Ubuntu used in that case. Let us put a scenario:
Sam has 11.04 updated until August. After that he simply decided not to keep updating the 11.04 packages. 11.10 arrives and now the big NEW 11.10 DISTRIBUTION VERSION AVAILABLE!!! DOWNLOAD NOW!! FREE WITH 2 BEERS FROM BRUNO PEREIRA!. So now Sam has 2 options, either update all packages of 11.04 and the upgrade to 11.10 or just upgrade to 11.10. What positive/negative feedback can Sam get with using one of the 2 forms.