Hashwell will get released in June this year, it has been confirmed by Intel. In my point of view that is worth waiting for, as it's not too long away.
AMD's next generation of CPUs we have no information on at this point, so that is a thing you shouldn't wait for.
AMD Radeon 8000 series is to be released in Q4 of this year or in early 2014. This information has been confirmed by AMD, as their sales was good with their Radeon 7000 series and they could get a lot of benifit out of it still. They also mentioned that it was because, they were going to spend their time on drivers and optimization instead. However I think that is a bad excuse, because they're working with PS4 right now, so they really can't focus on their next lineup as much as they wanted. So another one I wouldn't recommend waiting for.
Nvidia GTX 700 series is to be released in 2014. However it's not know when in 2014 as it is right now. Nvidia showed this information at PAX east, so it has been confirmed by Nvidia. Another one I wouldn't wait for.