Not for sure, but I would speculate Fedora will still be the top one. Ubuntu is the alternative.
I don't anticipate supporting other Ubuntu versions besides LTS unless they work with no additional platform changes. We just don't have the resources to update twice a year for Ubuntu. That is why we choose LTS, that way we can do it once and add features over time since it has 5 year support.
This is just my opinion, so to get the one that counts you need to ask the boss.
Fedora is only a test ground for Red Hat, how can you keep this as a #1 base for a server ?
Look at the trouble you had with Fedora 16. They move on and forget/neglect things. For example, the problem I had was that the new Gnome in F16 has changed power management. So if you are in runlevel 3 the desktop is not running and so the Power Switch does not work. Fedora 14 had slow samba transfers issues. Earlier versions had other issues. Crap like this happens much less on Ubuntu because Ubuntu is not a testbench.
PS: furthermore, your small team (which is doing a great job btw) is already overwhelmed, why support 2 bases (especially since Ubuntu is a serious release version OS and Fedora only a playground).
Other than the config files and base system structure they are both doing exactly the same thing.