I'd would hope that with a World Cup coming next summer, guys wouldn't turn down the Worlds just because they're bitter about being left off the Olympic roster. Burke has demonstrated in the past that he's willing to say "screw you" to guys that turn down the Worlds (a.l.a. Tim Connolly, who got left off even the Olympic orientation camp roster despite being one of our very best centers). I'm sure when it comes time to choose the roster for the World Cup, this will hurt Gilbert's chances.
I'm sure it would but if the World Cup is actually scheduled for next year (other than the original announcement in January of 2009 there's been nothing new on it) Gilbert's chances were already slim anyway. I was just speculating on Gilbert's potential excuse. Originally he was saying he hadn't be offered a spot yet and then apparently he was but he declined. If there was a more telling reason (say injury/wedding/child birth) I just figure he would have mentioned that from the get go. Gilbert certainly isn't doing himself any favors though, especially for the reasons you point out, and it seems like Burke will be leading Team USA for a good while as long as he wants the job.
But it's hard to say though at this point. There were a lot of declined offers for the last World Championships leading into the Olympic year and it probably hurt some and not others. For example, Gilbert apparently accepted a spot on last year's WC team and then declined and no reason was ever made public but he was still invited to the Olympic orientation camp. Guys like Connolly (injury), Malone (injury), Booth (no contract), and Quick (injury) declined as well. The fact is this tournament has never carried much weight with American hockey players. Hopefully with the NTDP and a lot of the pride we see in a lot of the young American talent that will change going forward but it is what it is.