So let's speculate on what the last 3 classes will be. There are 2 Sith and 1 Republic remaining.

One I am completely sold on for the Sith is "Imperial Agent" or something like that. Along with the recent comic issues putting this potential class on display, we have this leaked forum icon

http://www.swtor.com/sites/all/themes/swtor/en/assets/forum_76.png)

That pretty much all but confirms some kind of Sith Agent/Spy/Assassin class.

I do not think there will be any more force classes announced though I've seen quite a few people who still believe there will be.

For the other Sith class, I think there are a couple possibilities. I would still love to see some kind of Mandalorian class (yes I know they are a faction) but that seems to be getting more and more unlikely. The other possibility I see is some kind of Sith commando, heavily armored class.

For the last Republic class, I am either thinking some kind of Tech Specialist, or Spy. Really though, I am not satisfied with either of these ideas for the Republic, as they are just not anywhere as iconic as the other classes are, which is what BioWare is really going for. What do the rest of you think?

I think that the Sith are going to get a counter-smuggler spy/agent/assassin, and I think the final two classes are going to be a set of utility/support dudes, maybe tech specialists, but I think that Bioware will want something that matches their apparent 'Everyone pew pews' approach.

I thought about a combat medic type thing and then I thought why waste it? The bioware guys said they want epic. Well as much as I enjoy playing a healer in other MMOs, it's not my idea of epic. Plus they're leaving them for last...so they must be fairly interesting. They wouldn't want to announce healer as their last and final grand class. People would not be so thrilled.

They've got Warriors for each side (JEDI/SITH) - TANK/DPS
They've got heavy hitting ranged (Trooper/BH) - TANK/DPS
They've got stealth and non-conventional (Smuggler and likely Imp Intelligence) - DPS

What's the last archetype they're missing?
Sadly the only thing D&D thinking pulls up is a healer class, but I don't think they'll go that direction.

I 'unno, they might just go with healers, after all, tons of MMO's have.
Or maybe some cool hunter, it'd be awesome to have my own pet Acklay, although that might end up as a mount or something.

I dont Mind if they have a Beast Master Class, as Long as we go to Onderon to learn it, It's not far off the right era for it too, but apart from that I guess the Combat system will dictate the Class uses, names are just that.

IIRC Bioware said they don't want a pet class, and want to replace it with the companion system (ie. a pet for everyone).

Also, a little bird told me that the final classes will be aristocracy, bourgeoisie, and proletariat.

Quote from Darth Hater on last two classes (Sith Inquisitor and Jedi Consular):
We talked a lot today about being able to customize your classes in a number of different directions. When you think of Sith Inquisitor, you’re thinking about how we’re talking about him today in the Emperor Palpatine mold, the force lightning using guy. But as time goes on, we will show you other ways to customize that class that will give you a different gameplay style. We thought as core classes the Consular and the Inquisitor made the sense. We thought they balanced well against the other two. You can think of the Jedi Knight and the Sith Warrior as more of a melee-style Jedi, and the other two maybe more of the ranged-style Jedi. I think it made a lot of sense.