Macbook: now or later?

Usually Apple will include a free upgrade to new OS if you purchase the hardware one or few months before the new OS launch. The best way is wait for the new OS launch several months, then purchase new hardware. Usually there are a lot of bug fix and hardware incompatible issue when new OS launch. Price should be the same or slightly higher if you buy it after October. Better wait until December because a lot of bugs will be fix by then plus possible Christmas sale!