Definitely level up a lot of combinations, while you have RAF.

I did:
- Druids, Hunters, Priests, Shamans.

And had a month of RAF left, but did not use it for additional teams.
Since then, I wish I had done:
- Paladins, Mages and Warlocks.

Have actually started a Priest + 4x Warlock team (22nd).
And have been thinking of 5x Paladins and/or 5x Mages.
The druids RAF'd Boomkin, but are Feral so 5x Rogues are less tempting.

The DK's, weren't done during RAF.
But they're another team since then.

Nothing is wasted; even though the Hunters and Priests aren't played.
With the 4.x changes, Priests are quite fun and likely will be played.
They've both acted as 5 Transmute spec Alchemists.
Have made over 100k from each of the RAF teams, just during WotLK...

The more combinations, the more flexibility you have down the road.
I'm currently running these compositions; if any sound fun or interesting, it might be worthwhile leveling the relevant classes yourself (or if anyone else's combo sounds fun/interesting too).

- 5x Feral Druids
- 1x Disc Priest, 4x Frost DK's.
- 1x Blood DK, 1x Arcane Mage, 1x Resto Druid, 1x Resto Shaman, 1x Destro Warlock.
- 1x Prot/Holy Paladin, 4x Elem. Shaman.
- 1x Disc Priest, 4x Warlocks (spec undecided between Affliction/Demo).
- 5x Disc Priests (likely end up 4x Disc + 1x Tank)
- 5x BM Hunters

Druids, 84th, 525 Alchemy.
Priest/DK's, 80th, 485 Alchemy.
Mixed PvE, 80th, 485 Alchemy.
Prot/Shamans, 80th, 485 Alchemy.
Disc/Warlocks, 22nd, 0 Alchemy.
Priests, 75th, 485 Alchemy.
Hunters, 75th, 485 Alchemy.