"SQUEEZE FIRST ASK QUESTIONS LAST".
I've been through this many times before and it's a long and drawn out affair.
The bottom line is this: Buy, any Apple further down the line may be an improvement, but there will always be improvements and there's never really a definite pattern. Apple products are very good and no matter when you buy they will perform very well, with newer products never being anymore than 10% better than the last.