I don't believe Des killed him either...it is simply a way to get Locke and Jack back together - although I do think Des enjoyed it
. Of course Des isn't dead either...we see Sayid trying to put a bullet through him in the previews for next week.
What I believe will happen - and none of this is spoiler worthy cause it is just simply what I believe:
I believe there will be a real "sacrifice" that could take place on this show...and it ain't gonna lead to a happy ending.
Anyway, I think Jack and Juliette were married in the ATL and have a son together and of course Juliette dies on the island.
Hugo and Libby are together in the ATL. Libby dies on the island.
I think Sawyer and Kate get together in the ATL and Kate will die on the island - prolly attempting to kill Locke - or maybe just gets blown up with bad dynamite
.
Sayid and Shannon will, imo, get together in the ATL...are we starting to see a pattern here.
Penny, according to this pattern will die on the island as well.
What I haven't put together is the kid and how he plays into all of this...Perhaps he is a young smoke monster or a young Jacob...or whatever.
Anyway the last two shows are entitled What they died for. I think that means Des, Jack, Sawyer, Sayid, and Hugo die keeping MIB from leaving the island.
They might even have a choice...be happy in ATL or die saving the original time line...which might be kind of cool. Anyway that is my theory based on nothing but supposition and my preference for dark endings.