The answer is not a simple yes or no. The basic idea is: you can upgrade the base system and keep using the old pkgs just fine.
However, if you start later updating pkgs, it gets more tricky: you can keep updating binary pkgs build on the old (original) system version (or with a chroot setup and some tricks build localy). If you start building new/updated pkgs from source on the updated system, all bets are off and best practices say: start from scratch and rebuild all your pkgs. Martin
