Basically if the ipod is lacking features which 'you need' in order to enjoy it, then wait.
If those extra features are only supplemental and not fundamental then get one now.
iPad 2 will no doubt have a camera. Retina Display is highly unlikely. Remember if like the iphone it doubles the pixel density it would mean your 9.7" display would go from 1024 x 768 to 2048 x 1536 which is a considerable leap. The iPhone 4's 960 x 640 is still lower than the current iPad. So for the ipad to leap resolution would not only require a considerable bump in graphical power, CPU and therefore battery usage also. No one actually manufactures Retina Displays to anywhere close to that size, and therefore would require a massive leap for the manufacturers also. Something which is highly unlikely to be here in 12 months let alone 6, and then the cost would be considerably higher too.
The reality is a 10-20% mhz boost in CPU & GPU, internal mem upgraded to 512mb and a camera are the iPad 2's most likely advances.
With the ipad still not launched globally, and only the third wave of countries in line for the end of July, with more to come and of course the ipad's first 'holiday season' - the chances also of new refreshed ipad devices in Jan are very slim. If anything it will be April / June 2011.
9.7" retina displays are way off in the horizon.