First reaction: "Oh, that guy was right." There was a post here on Enworld a few weeks before where someone complained "What is Monte doing at WotC? He must be working on a new edition"
Second reaction: "Are they nuts?" There should be at least 8 years between each big number, simply because each edition takes a while to mature.
Third reaction: "Ok, let's check it out" Well, turns out there is absolutely nothing out there except "we're working on it".
Fourth reaction: "Don't screw this up again." I like 4E as a game, but there were so many screwups in the announcement and everything that I just didn't have faith that they would do a decent job this time.
Fifth reaction: "How would I do it?" This is where the geek kicked in. It's unlikely that 5E will be exactly like I would do it, but it's going to be interesting to compare.
Sixth reaction: "Let's see what others think" Hit the boards and read threads. This is where I am right now.