After the commercial disappointment of Aliens Vs Predator Requiem, it seems that Fox is now looking at these two franchises in a new way, kind of.  It seems that each of them is a getting the 'reboot' treatment now.

First there was Predator, with Robert Rodriguez being asked to give the franchise a new start.  Rodriguez had previously written a potential squeal to the original movie, which he called Predators - it seems that while the movie won't follow this script, the tone/feel of the script is being used a guide for the new script, so this is definitely one to watch for.
For more information on this have a look at the follow links

News Story
http://www.aintitcool.com/node/40865
Rodriguez interview
http://www.aintitcool.com/node/40879

Then, today, news broke that an Aliens 'reboot' is also being pursued.  Not so much is know about this one other than the intention is bring back the tension of the first Alien movie by only having a single Alien and, possibly the most important part for everyone wanting a faithful movie, Ridley Scott (director of Alien) is on board as producer for the movie.

http://www.empireonline.com/news/story.asp?NID=24916

One thing that let's me breathe a sign of relief about both of these 'reboots' is that it seems that neither of them are trying to start from scratch and ignore everything that has happened already, both movies will fit into their respective franchises - or at least that seems to be the intention so far, fingers crossed it stays that way. 
Potentially both movies could have relatively close release dates (though, despite this posts title, they won't be going against each other at the box office since they are both by Fox..), possibly next year for Predators.