Was hoping for something for something a little more exact than a 3 month window
i dont recommend you to take business decision based on that.
personally i expect 2016 1q for product to be widely available and 2016 q2 to initial issues with products to be solved.
For actual projects to have a concurrent dual band AC ap its necessary to assemble a rb922 with an additional 2.4ghz card, 4 antennas, power supply, poe injector and proper case, cost 200 US aprox.
i know is a shame that mikrotik have waited too long to do that products, looks like WLAN market is not the priority for mikrotik, looks like they are focused primarily on outdoor wireless.
Entering 1 year late to 802.11ac WLAN market is not a good thing, in my country its a total nightmare to get the necessary parts to assemble a dual band mikrotik ap and many customers have opted to buy products like ubiquiti unifi because of that.
Its difficult to fight and defend miktotik as a respectable wireless technologies brand in front of customers when they see that mikrotik do not has a dual band 802.11ac wlan accesspoint.
I do not understand why mikrotik waste effort making the cap2n based on that anemic radio, making the cap2n with a radio like 951Ui will be nice very nice.
And again making the same mistake, a lot of hAP without any case with a proper appearance to be attached on a ceiling.
I do not understand why mikrotik think on products like rb951 to be only as a home or small office equipment and not as a AP for projects with 10s or even 100s or even 1000s of AP.
I found mikrotik products very capable for wlan environments, i have very successful stories with rb951Ui rb951G and even the anemic rb9512n, but the physical appearance of equipment and the lack of integrated concurrent dual band its a issue more serious every day.