Upgrade to Mx 5, how to deal with branches?

We are planning a Mx5 upgrade (from 4.8.3.). I was wondering whether there are best practices when it comes to migrating active branches? The obvious answer is to merge them before migrating, but I don't know if this is manageble. Thanks!
1 answers

As an experiment I would try upgrading 2 (new) branches and merging them to see if the merge includes the same differences as in Mx4 or something more.