If you can find a price you are comfortable with I'd go ahead and book. I go to WDW several times a year and I've noticed that airfare is just alot higher this year than what I'm used to paying. I pretty much always have a trip or two in the planning mode, so am always checking airfare. For my Sept and Dec trips airfare has been running around $298.00-$400.00+. Two weeks ago when Southwest put their fares on sale, so did American. I was able to grab fares for $270.00 for my Sept trip and $245.80 for our Dec trip through American. They stayed at those prices for several days, before jumping up again. I just checked and the exact same airfare for my Sept trip is now $298.80 and then $413.80 for our Dec trip. I'm glad I grabbed them when I did.
The same thing happened for our May trip. About six months before the trip, fares dropped down to around $270.00, so I grabbed them. I then checked pretty much daily just to see what they would do. They never did go down again. Fares used to drop a couple of months out, but they don't seem to do that anymore. Prior to the last year (maybe 1 1/2 years), I never paid over $200.00 r/t, but I think those days are now long gone.