It has been very hard to predict when Amazon will release a new Reader. In the past they have actually done so later than many people expected. There could be one released at any time, but the fact that the K2 is now on sale at Target argues against it being replaced any time soon. This also argues against them lowering the price in the near term, which I half expected.
Don't forget that if you buy direct from Amazon you essentially have a 30 day window after you buy when you will get back any price reduction and/or you can return the K2 for a (say) K3 if it is announced.