Hello,
So, I have been thinking a bit about where things are going to go with the show.
A few theories (and I may well be very wrong):
1) Cylon is the term for those who believe in a single, monotheistic deity. It has nothing to do with mechanical or biological ideas. The mechanical cylons were designated as such when created and when the human form models began exploring concepts of divinity and a monotheistic god the connection was made.
Consider that we know Tyrol had a father who was a priest, but he rejected his father and religion. Best to call him an atheist or lapsed believer in the 12 Lords of Kobol for most of the series. We also know that Tigh is not a religious man, as evidenced by many conversations with Adama about the President's religious ideas in the late 1st and early 2nd seasons. We don't know as much about Anders or Tory, but perhaps they are in the same boat. They do seem to be pragmatic individuals (especially Tory's focus on political realities and vote rigging instead of faith in the electorate when Baltar was elected).
They become "cylons" in the episode by having a religious awakening, foreshadowed by the music. The music representing their inner journey towards a more spiritual state of being. We certainly do see more focus and dedicate to duty and values by the end of the episode than we have seen for quite a long time in some of them. Tigh is the best example here with his self pity and drinking, Tyrol to a lesser extent with his personal conflicts around family life and being back in space after resigning, Tory in the one episode example of poor performance to the president [very little, and poor lead up in my opinion], and Anders obviously has been working through issues related to Kara since the love quadrangle developed and possibly even before that. Her death caused change in his life (pilot candidate right after), but was that simple compensation rather than any real dedication or belief?
So the four revealed in the episode can be cylons, without being mechanical or even human form copies like 6.
2) Of course, as mentioned above, Anders could be the one seen by D'Anna in the Temple of the Five. She did try to kill him once and that would be something to apologize for. If he is a cylon of the human form type it would make sense. Reconciling the rest would be harder to do (Tigh being the toughest in my book, Tyrol the second hardest).
3) The Beings of Light will factor in some how, but I suspect that in a manner we are totally not expecting. I do not expect it to mirror the original series, except in the most general of details.
4) I suspect the cylons in the nebula are real, and of the regular mechanical and organic varieties. The cylons in the series have been shown to be quite smart. I am sure they figured out the refinery ship trick. In fact, with the superior jump capability of the cylons they likely could jump to several systems ahead of the colonials and some of them (the Cavills likely) could figure out the symbolism of the nebula insignia.
Cheers