Google Chrome is a unique web browsing experience, since not only is it a popular browser by a search company, it also is able to completely and competently power a number of laptops known as Chromebooks. But what it does is unique because it works on all OS' with Chrome installed, and that is apps. Native apps. For Chrome, by developers. Made specifically to work on computers instead of just porting them over from tablets and phones.
But the support for specific types, namely the legacy packaged apps, will be left out of and removed from the Chrome Web Store, but also that these apps can no longer be published to the store. The removal of these apps will occur in December 2014, and the compatibility with Chrome will stop in June of 2015.
What this means is that Chrome is getting an important update in June of 2015, and that the apps that Google wants on the Chrome platform will be improved in software base and will likely be compatible for far longer than the current apps. But the important part for developers is that they are able to update their apps to ensure compatibility with the policy and store.
What's interesting is that Google notes the depreciation of these apps. Depreciation, for those not versed in economics, or who find it inconvenient to look it up, means losing value as time goes on. Google sees less interest, leading to fewer downloads, and therefore less revenue and profits from the apps than before and as time goes by. Another thing to note is the removal of the unaltered apps, the ones that the developer(s) haven't or don't update(d) will not be a full removal from servers or the like, but a removal of the apps showing up in searches or browsing lists in December.
Google do, instead of leaving their many developers to flounder and upgrade their apps and extensions on their own, offer up a guide on how to go about the process. If you happen to be a developer of one or more Chrome apps and extensions go check that out, and if not, hope that the developer(s) of your favorite apps and extensions go through the process to continue support and downloads of their software.