Lets just drop all the "love to see Angel dust Spike" or "love to see Spike kill Angel" acts and in fact focus on what a good ending for the show is.
Personly id like to see Angel come back to Sunnydale, having fullfilled his Destiny and become human again as the prophecy stated. Buffy would know this but is know in love with and together with Spike, quickly a triangle drama appears as Angel and Spike are rivals of Buffys love. But in the end Buffy wont choose either of them because she cannot make the decission between two people she loves.
However James Marsters has stated in an interview there will be a very romantic ending between Buffy & Spike that will psis some fans off. He did not go into detail but that appears to show that either he sacrifices himself for her, or she picks him in front of Angel. Because face the facts, its not romantic between them if she picks Angel 😉
Anyways for Buffys ending to be, it should be an epic battle (buffyverse epic) between good and evil, and it will probably end with Faith sacrificing herself to save the world. To redeem all the evil she has done, and because she wants to be a better person and wants to be loved, accepted and respected.
I think that nobody will really die in the ending except for extras and SITs 😀