As one who waited and waited and then waited some more... I'm not exactly sure what to do other than wait for even more.
The time you've already spent waiting is what's know as a sunk cost. Meaning, the time you've spent waiting is irretrievable. According to economic theory, sunk costs shouldn't be factored into buying and spending decisions at all, the only thing that counts is what's the best decision you can make from your current position that leads to the best outcome.
For instance, let's say you go to see a movie and you pay $12 for your ticket. After sitting through half the movie you feel like watching the movie is torture and you want to walk out, but since the theater has a strict no refund policy, you feel like you have to sit through the rest of the terrible movie so you can "get your money's worth" otherwise you'd be "wasting" $6.
But that's an incorrect description of your situation, because all $12 dollars have already been spent no matter how you decide to occupy your time afterwards. So the only decision you have any control over is how you spend the next 45 minutes of your life. Do you spend it suffering through a terrible movie, or do you walk out and go catch a tv show at home? Either way, you're still out $12, but one way is torture and one is pleasant.
So the amount of time you've already waited for the new Macs shouldn't enter into your decision, because you can't get that time back. The only question that you should ask is the only one that you have control over -
- Is now a good time for me to buy a Mac?
If you decide to wait even more, that means more time without having a new mac, and all the consequences that entails. For instance, if you run a business on your machine and it's getting slow for your demands and thus lowers your productivity, you have to consider the amount of work lost in lower productivity between now and when you finally get a new mac to work on.
The only caveat to this logical perspective is the emotional perspective. Sure, if it makes monetary sense to buy a new mac now, that's a great reason to buy right now, but if you think having new macs come out in a few months will significantly impact your enjoyment of the computer you bought, then you should take that into consideration.
So this is the second (2 part) question you might want to consider;
A) How long a gap between when I buy a computer and when newer models come out would I be satisfied with?
B) Do I think newer models will be released before that length of time?
http://en.wikipedia.org/wiki/Sunk_cost