Lee Badman comments:

Two points to consider beyond just when you move to the next great thing in WLAN:

–  Many of us have invested hundreds or  thousands  of cable runs in our current wireless networks, each supporting up to 1 Gbps. …  How drastic does our “investment” in our installed cable change with 11ac? Surely, a single 1 Gig uplink won’t be enough for an 11ac AP.

–  There is no free lunch for any technology. To get to the promised data rates of 6.9 Gbps for the second-wave of 11ac, we’ll need to use crazy wide channels and reduce the 5 GHz spectrum to potentially the same state of overuse as 2.4 GHz suffers now (even if the FCC burps up more spectrum).

Read more at: So- How Much Interference And How Many Wires Would You Like With Your 802.11ac?