Opinions on Newhall Ranch development effect on home values?

[Ryan Sommer]

Apparently this is getting approved and moving forward and there will be 5500 new homes built right by Magic Mountain and 21,500 total units including business space, retail, elementary school, fire station etc

http://www.dailynews.com/government-and-politics/2...

I just bought a condo last year in an expensive market that is about a mile away from where this will be and trying to get a feel about whether or no I should be concerned about value of my place?  My condo is work about $30k more then I paid last year but will $350-400k condos correct to $200k with influx of new construction?  Will all of the $800k houses in my neighborhood be selling for $400k in a few years?  I know that nobody can predict the future or markets but seems like that many new homes at once could greatly effect the market values.  But on the other side I know that if it leads to more businesses there and more jobs then the area could potentially boom too.