In the farm I'm looking at, there are some old archive-like sites that were upgraded from a 2007 farm to a 2010 farm but still have the V3 UI. Some of them are heavily branded, not actively used, some even read-only, but they are still searchable and available. There is no way any effort will be put into updating them to a new look.
Now it's time to look at migrating this same farm to SP2013. As we know, the SP2013 farm has both the 14 and the 15 hive, and we can move 2010 Content DBs to the 2013 farm without upgrading them to the 15 hive.
My question is: Will I be able to keep these webs with the V3 UI on the 14 hive of the new 2013 farm? Has anyone done it? Any caveats I should be aware of?