I think it is supposed to be ready for the 2009 season.
He got a 3 year contract with an option for a 4th....so, unless he does a really bad job, he should be here for at least the first year.
However, I think Jerry Jones would NOT want to go into the new stadium with a team that has gone 8-8 or worse...so I have a feeling unless Wade Phillips does at least as well, if not better than Parcells' record of 1 playoff game, no wins...
He may be replaced by someone that first year...because it is a HUGH stadium with a lot of seats..and a lot of suites, and it will be a lot harder to sell season's tickets and suites for a losing team, with boring coach.
The Cowboys not only WON..but were never boring when Jimmy Johnson was the coach...and then that one year that Barry Switzer took them to the Super Bowl and won...LOL