id just hate to buy it then already have a product that's a generation behind
If the 600EX-RT does all that you want it to do, what difference does it make if it is 1 or 2 "generations" old? Pretty much everything in photography will be replaced. Since companies recognize that novelty has a value in itself, new models will be coming out more often.
Trying to keep up with the current generation of any type of equipment can become expensive and may not really give you any real advantage.
The best time to buy any photographic equipment is always 2 years from now... but following that "logic", you would never buy anything.
If the 600EX-RT does what you need it to do and you feel you need multiple flashes, buy them now if they are at a good price. Waiting around in case there is a new model coming out (which Canon has not even mentioned) does not make sense.
Now, if the 600EX-RT does not do what you want, and you are willing to gamble that any future models will have the capability you need, then by all means wait.