yea i agree stalker, mostly throughout the movie a sense of time is not shown, however this scene is the only one that gives an idea how much time p relative to the storyline.
The lifecycle was sped up by the chemicals pumped into the queen, this may have shortened the comatose state, although since it lasted less than 10 minutes (judged by the pyramid reconfiguration time) I'm assuming that it may have also been to just speed the pace of the movie up
Posably becaus of the Predators phisyolgy (sorry spelling) it may not hafe reactid the same way as a human would becaus there genoraly toufer than a human would also explain how it toock so long fore that alien to emerge from him
or it could be that the chestburster had a hard time getting around in hid chest and maby struggled to get out.i still think that that was another mistake by anderson even though the predalien was sweet,they shouldnt of put it in the main predator at least