If I remember correctly, last fall there was a fairly good sale on exec seats to LHR and some other destinations as this is a low season for such fares. Sun destinations will be peak season at this time, so I doubt there will be any big sales.

Who knows what fall sales there will be this year. As stated before, if you find a fare you're comortable with, buy it. It is like the stock market; the price may go up or down after you buy.