Thanks for the spoiler, ****.
Uh, the developers have stated this, said it was a big decision and all, so not a spoiler at all.
http://www.vg247.com/2012/07/28/dianas-death-is-a-catalyst-for-agent-47s-actions-in-hitman-absolution/
Rather disappointed that she does die though, she and 47 (and I guess Smith) were one of those nice constants through the series.