From what I understand, the problem with running local apps on Chrome OS has been the lack of a storage manager, because the original assumption was that all data would reside in the cloud. Many Android apps require local storage so Chrome OS could not support them. That is supposedly going to change by the end of this year with a local storage manager being implemented in Chrome OS. Apparently this requires some kind of hardware support, which means older (and less powerful) Chromebooks probably can’t use it, so Chrome apps will continue to be supported by Chrome OS “for the foreseeable future” according to Google. How foreseeable is anyone’s guess.
Eventually, Google expects most, if not all, Android apps to work with Chrome OS and I would guess that at that point ONLY Android apps will be supported on all Google platforms.
The idea here is to have a single store through which all apps are distributed, which is also what Apple is trying to accomplish with the convergence of iOS and MacOS, and I suspect is also where Microsoft expects to go with Windows 10 (probably justified as for “security” purposes). This will allow Google/Apple/Microsoft to monetize their operating systems by collecting a tax on every app sold.