I have read all the theories but I still believe that

[MBurrell91 5]

The seven guardians of light are still going to be:

Sora, Riku, Kairi, Terra, Ven, Aqua, and Lea. 

 

Not sure where Mickey is going to fit but I just feel in my heart that these are going to be our seven lights

[Moni_22 335]

As much as I love Lea, I think Mickey takes his place, I don't see a reason why he wouldn't be one. Lea has his own objectives, he doesn't need to be one of the 7 Lights

[KH4Real 749]

Mickey has said who the lights are but Terra belongs to Xehanort (Terranort).
I say those will be the lights:

1. Sora
2. Riku
3. Kairi
4. Mickey
5. Aqua
6. Lea
7. Ventus or Ling Will

It may depends if Nomura let us choose to save Aqua then the Lingering Will could take her place.

[Allwil13 754]

I definitely think Ventus will be one of them, but I don't think all three of the BBS trio will be part of the 7 Lights. I think either Terra or Aqua will be somehow incapacitated for the final battle. I also think that Roxas could be one of the 7 lights, but if he is then he'll probably replace Ventus. I think it will be the following:

1. Sora
2. Riku
3. Kairi
4. Aqua/Terra
5. Ventus/Roxas
6. Lea
7. Mickey