Thanksgiving flights -- to book or not to book?

Air fares are so (relatively!) low right now that I'm strongly considering taking my kids back to the States for Thanksgiving this year.  I'm torn between booking now and waiting to see if the prices will drop lower, though... I know that fares traditionally tend to drop after Labor Day, but am having a hard time believing that London - NY is ever going to get much cheaper than the 280-or-so pounds that BA and Virgin are asking for a return trip right now.

It's all a game of chicken, I suppose, but I thought I'd try to see if there's any conventional wisdom from those who have been at this UK-US flight booking thing for longer than I.  Would you snatch these fares up or wait and watch for a while longer?

Well I recently booked for flights back to the US for Thanksgiving with Delta from Gatwick to Atlanta for two adults and two children for £1023. I didn't expect them to be that cheap and didn't want to risk prices going up so I booked as I figured it was far cheaper than I expected anyways. 

I booked my flight already as well (on Virgin) in last week or so and I just checked the dates again and the price is £20 more than what I paid. You can still get tickets to New York for about £260 return depending on your dates. I don't think they'll drop much further.

I've been going back for Thanksgiving for the past 3 years and the lowest I've paid is £230 -- which Virgin was offering when I booked this year but the combination of flight times and airports Newark/JFK for that ticket didn't work for me. (Last year I paid £298)