There was a http://www.gamesas.com/index.php?/topic/1150885-fire-propagation-like-in-farcry2/, but hopefully the moderators will deem your poll awesome enough to justify a second related thread.
I voted yes across the board, though as I posted in that other thread, exactly what is affected, and how much, might need to be limited to preserve sanity and some semblance of balance (ie, briefly setting a tree's branches aflame with a poorly aimed fireball would be great; setting the entire forest on fire and killing every creature and NPC within a 300ft. radius, not so much).