I have a feeling Cordelia is the Supreme.
Next to her name in the title sequence is 'Santa Muerte', the female personification of death, protection, healing, and safe delivery to the afterlife. She concerns herself solely with protecting the coven, and in episode eleven she 
"makes a desperate sacrifice to protect the coven"
 according to the mini-synopsis, and her extensive knowledge in botany symbolises growth and replenishment i.e healing. The "safe delivery to the afterlife" hasn't been explicitly shown yet, but it may foreshadow her role in Fiona's downfall. Ryan Murphy says it 
gets worse before it gets better
, and the 
new Supreme rises
 in episode thirteen, which could potentially allude to her taking the throne. I feel like the word 'rises' is too dramatic for it not to allude to Cordelia defying the odds. 
Another name for 'Santa Muerte' is 'The Lady of the Seven Powers'.
It would be the perfect end to her arc. I would be personally disappointed if, after her midlife crisis, what with Hank's death, doubt in her own strength, loss of good graces with her mother, and the 
imminent danger that befalls the coven, as per a vision
 in episode eleven, suddenly surging with power could compensate for all of her losses. I suspect she'll 
lose her eyes as a desperate sacrifice to regain retrovision
 next episode, which compromises her health, thus disqualifying her, at least the criterion for "perfect health". 
Considering she 
has a vision of the future next episode, whereas she could see the past when she was blind
 she might gain some new, simply omniscient, powers.
I might add, why the **** did Nan die? She was showing so much potential and they just kill her off. It could have been prevented if she hadn't been such an uppity bitch around Laveau, and had just given her the baby rather than boasting about Supremacy.