You're looking at it backwards though. It has been reported on many sites that class is selected first, and then your race as part of your classes "backstory". It is very much "smugglers can be twi'leks" and very much not "twi'leks can be smugglers".
Right Class then Species because every class will have their own selection of species. However, as Limess has stated, BioWare has stated numerous times that some species will be available to numerous classes. Looks what they've done so far.
Human - All
Twi'lek - Smuggler
Miraluka - Jedi Knight
Mirialan - Jedi Consular
??????? - Trooper
Zabrak - Sith Inquisitor
Sith Pureblood - Sith Warrior
Rattataki - Bounty Hunter
Chiss - Imperial Agent
Because each class has their own stable of species, they are announcing one for each first, that way every class gets to know something. Troopers of course are getting the shaft being the last ones. Let's take a look at a few of these species though and what other classes might be available to them. Keep in mind that BioWare likes to go with Iconic images.
Zabrak - Who is the most famous Zabrak in the EU outside of Darth Maul? Bao-Dur from KOTOR 2. Expect a Zabrak Trooper
Rattataki - The only image many people have of the Rattatai is that of Asaji Ventriss. Ventriss was a fallen Padawan scooped up by Dooku after her master died and she gave into hate. Expect this species to be playable by Sith Warrior and Jedi Knight as Ventriss is famous for her dual sabers.
Twi'lek - See previous post. I believe Twi'leks will be open to Smuggler, Bounty Hunter and at least 1 Jedi and 1 Sith Class.
Mirialans - I know of three Mirialans, 2 (Luminara Unduli and Bariss Ofee) would be considered Consulars (got that one covered) the other is Hylo Visz from the timeline videos. Expect a Mirialan Smuggler. In Fatal Alliance the Agent was a near-human. While not a Mirialan. Part of the story dealt with how he was an outcast even as an agent of the Empire for not being fully human. It's easy to see a Mirialan in a similar position as an Agent.
Miraluka - These force sensitive people have historically been followers of the light. However, after the mass murder of so many of their people on the colony world of Katarr, it's easy to imagine them as a Sith (see Visas Marr, KOTOR 2)
Sith Pureblood - For obvious reasons, I see this species restricted to the Sith Classes
Chiss - For sentimental lore reasons (Thrawn) I see this species being one of the few one class species. To be a Chiss, you're gonna need to be an Agent.
That's my 2 credits on the species so far. Of course, I've been wrong before. Take if for what you will.