Based upon simple deduction we can draw some pretty big conclusions from some of the visuals we've been given since Battlestar Galactica returned for Season 4.5 The most noticeable change has been the shift from black to white.
All logo and promo materials have always featured a black background, until 4.5 - the sequence of episodes composing the final arc of the story.
Now it is a white background which is featured in the promo materials and the appearance of a light blue colored light as a transition element. Since in the past most of the overall story mirrors the original series and what is teased in trailers and leaked as promo material spoiler images actually occurs in eps (if a bit out-of-sequence) we should expect what we are being shown now has meaning and that it comports with the original series and earlier story of this incarnation of BSG. Thematically I believe we can expect an ending that ends with light - literally and figuratively. It will be studied bleakness until the last moments, however.
[stop now if you don't want the ending to be spoiled - I have no inside info, just the application of simple deduction - Highlight for biggest potential spoiler]
>>I believe they are actually going to bring the Ship of Lights subplot from the original series into their version of the story. I believe this blue light is visual foreshadowing, and the many many references in the dialog throughout the series to the One True God (and "someone or some thing is orchestrating all this") will be wrapped up in this way. Just look at how well the fit is between the original Ship of Lights and this screen-cap of the blue-light transition. <<
Roslin will be reborn - as we have seen in these images (the last shot for the series I believe) - unless it is a flashback to a free-spirited moment she had after her cancer diagnosis on Caprica (and if that were the case it would have merited some mention that she had made a public spectacle of herself prior to her appearance at the Galactica decommissioning ceremony as a Cabinet official of the government).
If the end is the beginning, then perhaps our characters are returned to pivotal times and places [by the One True God] - but with the knowledge giving them the choice not to let the cycle repeat. That would be a mystical ending with the thematic heft to close the loop of the overall story.
We see a happy couple, Baltar and Caprica Six (is this the actors out-of-character or a lighter moment between the conspirators of the Colonies' demise?), in different outfits than in the scenes form the miniseries at this location. Does it reference a different meeting from the era of the mini, or is it "new?"
Adama and Roslin are together in this green-screen shot in a Raptor - so was it cut, or is it from before Roslin dies?
This shot of Lee greiving is a promo still from Islanded In A Stream of Stars and the weight of his sorrow and formal attire of those assembled denotes a high rank indeed for the deceased. Only Roslin, Kara or his father could evoke such grief from Lee. Most likely it is Roslin, since he seems to bear the weight of the world on his shoulders as he performs here.
It seems not likely at all that Kara will die in the episode where we finally seem about to learn her true nature after the set-up in Someone To Watch Over Me. It would be bold to have Roslin die so simply at the end of STWOM - a reaction to Hera's abduction. It doesn't make much sense, but it would be bold.
Kara has been told by the rebel Hybrid that she is the, "harbinger of death" and the Old Hybrid said, "not an end, but a beginning."
So, with the blending now introduced into the story it seems that the "end" represents the end of difference between human and Cylon as they become a blended people.