I read this, novoted, came back and read it again, and am now upvoting. A couple of things kept me on the fence:
It might help this article to hint at the existence of other such eggs. Who/whatever made this egg would have to know just one egg would be unlikely to repopulate the entire planet, leading me to believe there would be others (your skip though, so tell me if I am incorrect).
Again, I am basing this on my perception of the creator(s) of this object, but something besides popping organisms into existence might happen, to aid in distribution of these things. Maybe it affects local weather patterns to increase rainfall and cause high winds to aid in seed dispersal? Maybe it causes some sort of reproductive/and or nomadic compulsions in reptilian/avian lifeforms?
Overall I liked the concept enough to upvote, but I just feel like a thing capable of making this object would put more sophisticated means in place to make it successful in its implied purpose.