Enterprise-class 802.11ac products won't appear in great numbers until around the middle of the year. But the handwriting is regardless on the wall - .11ac will indeed replace, over the next five years or so, 802.11n. That being said, I'm still encouraging clients to purchase 802.11n products if ROI, however measured, can be demonstrated over the next two years - and that's usually not a difficult task.
But there's actually a good deal more the enterprise needs to do to get ready for 802.11ac, primarily with respect to planning, upgrading the wired network, and projecting demand in the outyears. With the WLAN now essential in most organizations - a far cry from the "nice to have" of only a few years ago - the impact of all that Wi-Fi traffic on the wired network can be overwhelming without proper planning and operations. Keep in mind that, while I expect many common 802.11ac implementations to push into the 500 Mbps range (L7), .11ac is not really about throughput - rather, it extends capacity by making more efficient use of the airwaves. So even if gigabit-class throughput isn't a requirement for many applications, .11ac will, properly deployed, address the rapidly-increasing traffic demands of today's multi-service, multi-device, BYOD reality.
And since the wired network provides interconnect and backhaul for all those APs, it is key to that proper deployment of .11ac. This is such a broad subject, in fact, that we've just published a new Farpoint Group Technical Note on getting ready for .11ac (special thanks to Aruba Networks for hosting this). There's a good deal of both background information as well as practical advice (based, in fact, on what we're doing to get ready for .11ac) here, along with a helpful checklist of key recommended activities. I hope you find this useful - I know I have. And we'll of course have much more on .11ac as the year progresses. For now, though, get ready - I expect a good number of you to have at least partial 802.11ac implementations in place by this time next year.
Best wishes for the New Year to all - and it's going to be another big one for wireless and mobile.