My only specific info is for US; their policy was put in place on March 18 with a declared expiration date of June 17. I don't see that they'd end it sooner (though I guess they could if they wanted to). I too invoked "Peace of Mind" more for reasons of convenience than war fears for a London trip that fell too close to an important work deadline. I cancelled via US's online form and then called to reschedule for 3 weeks later.

If you'll miss the Iraq War flexible policy, fear not, for there is now a CDC Alert flexible policy.

Interestingly, the term "Travel Alert" from the CDC seems only to apply to Toronto. Other Asian destinations only have a "Travel Advisory" (not that US would fly there directly).