I don't consider changing from cromoly to carbon an "upgrade." I've heard of and seen many shattered carbon forks. I've never heard of or seen a shattered cromoly fork.

A shattered fork can cause a fatal accident (there's at least one thread here in bikeforums about a fatal accident when the carbon forks shattered), and if it doesn't you're almost certainly going to do a face plant, with accompanying severe injuries. If it was me, I would keep the cromoly fork.

That's my opinion. Of course, other people may have their own opinions.