I have just answered that question on joans_journal
... and my thoughts are ..."I love some of the fics where they are offered an eternal choice - so they fight together for many years - then given peace together!
But yes, Buffy dying will be with Spike at her side - either he dusts and she hesitates; or she dies and he meets the next sunrise."
Sorry for all those non-Spuffy fans, but they are together in my mind (no, I haven't read a single comic); their story takes off from "Chosen", with a bit of AtS season 5 ... and they find each other, and move on, together!
I still haven't had time to get back to my re-watch, but my overall memory of their journey is one of steps ... hard steps. Those mean that they have a real relationship ... and that they should be together, whatever life throws at them.
So, what are your thoughts?