Hi,
Also not every one lives in crowded urban area. Think about ranchers, farmers, etc.
Or just people who live on the outskirts. I am neither of the above professions, but on my 1.01 acres I see 4-5 other SSIDs walking around my house. The strongest hits -85dBm. IE, basically non-existant. Even outside my house unless I walk up on a property line none of the them hit over about -75dBm.
I haven't tested any of it, but it might be possible that you get better usable speeds on 2.4GHz 256QAM 40MHz than you could on 5GHz 80MHz 256QAM...but probably not. I can see instances where it would be a nice feature for a wireless backhaul on a mesh network and using 5GHz to connect to the clients.
There ARE use cases where it can be nice, but they aren't big.
As for 10GbE in a router, it is needed sooner or later. That or link aggregation.
The upcoming 4:4 160MHz 11ac routers will deffinitely be able to push more than 1Gbps of payload data over the airwaves on connections, add in MU:MIMO and scenarios where they might actually have use cases that cause that are increasingly likely.
So, 10GbE in a router...no, but link aggregation, it is needed sooner rather than later. Plenty of 3:3 80MHz pushing 400-600Mbps usable speeds on 3:3 links...add another and double the bandwidth and you'll certainly be maxing the 1Gbps wire speeds.
Will most people need that? Hell no. It would still be nice to have and 802.3ad should add pretty much nothing to the cost of the router, just firmware and as an L3/4/7 device, a router should easily be able to handle link aggregation. Heck, my semi-managed L2 switch does it just fine all day long.