> nobody cares about IPv6 except for us tech nerds
Nobody cares that your app is written in Rails of NodeJS. People care that it works and does what matters to them. IPv4 is doomed to not work at some point so we "tech nerds" have to care and do something about it.
> IPv6 is used by nobody
From the top of my mind, many of the french ISPs have IPv6 ready on the customer side, a radio button click away, while some are even on by default. I can readily assume that today, every worthwhile machine connected to a LAN supports at least IPv6 local scope. Also, every single Mac out there uses an IPv6 VPN (over IPwhatever) when (at least) Back to my Mac is active (ifconfig utun0).
> in five years it will still be nowhere
Unless you settle for impractical definitions of "nowhere" as "not ubiquitous", it is definitely there already. IPv6 does solve real problems today, locally and globally.
> From the top of my mind, many of the french ISPs have IPv6 ready on the customer side, a radio button click away, while some are even on by default.
I think this is one of the key points that certain people end up missing.
Windows Vista and later can do IPv6 by default, recent versions of OS X will do it by default as well. All an ISP needs to do is send a user a router which can handle IPv6 traffic - and suddenly the entire network will start doing IPv6 traffic with places like Google who are IPv6 ready.
It will just happen! Add the IPv6 ready equipment and the traffic will flow. The only problem is certain ISPs who are still stuck with their heads in sand, not providing IPv6 connectivity, and still providing customers equipment which can't deal with IPv6 traffic - some of which might not be possible to upgrade.
I actually expect it to accelerate. Once it has significant takeup you start to look bad if you don't support it, which will add to the drivers for ISPs to implement it.
I know of several German ISPs (Kabel Deutschland, MNet) that don't even give you a dynamic IPv4 IP anymore, but use Dual-Stack Lite (that is, IPv6, and carrier-grade NAT to access public IPv4 addresses). Oh, and they limit the ports (and thus connections) you can have open at a time, to something like 1000. I wouldn't want to have such a connection.
If you intend to host your service behind something like CloudFlair it doesn't matter that some users don't have IPv6 yet: they'll contact the cache service via IPv4 and it'll contact your servers as needed via IPv6. The end user doesn't have to care, or even know at all, and you have just made a saving by not having to pay for IPv4 addresses.
People will start to care when IPv6 takeup hits critical mass and we start seeing services optimised for it. When people start seeing services they want to use not working as well through layers of NAT, they start asking their ISPs why they are having a problem and their friends on other ISPs aren't. Maybe at some point services will start charging a premium for IPv4 access (so IPv6 users aren't subsidising those who haven't moved forward yet) like on retail business did for IE6/7 users (http://www.bbc.co.uk/news/technology-18440979) then people will care. That seems extreme though and might alienate users, less severe option would be to serve more adverts.
There are some places where things are already heading towards being IPv6 only. A friend of mine noticed this when out east for a work related trip, the hotel he was in provided Internet access but IPv6 only internally. They provided a 6-to-4 gateway so IPv4 only sites worked fine (with everyone from several places looking to be coming from the same address) but your device had to speak IPv6 to connect to the network in the first place (which his phone didn't).
I'm just waiting for when we get to the point where there are thousands of users behind the same ipv4 address and one of them gets the ip banned from something popular. I'm sure customers would start caring then.
Or worse, someone does something incredibly wrong from that address (arranges a bombing, posts kiddy porn, or so forth) and the police arrest everybody associated with the address just-in-case...
In same way, no one except 'us tech nerds' care about IPv4. Why would anyone who does not have to work with it, or have an interest in tech, care about protocols?
(For what it's worth, I should disclose the fact that I work for Gandi, as requested by a colleague wrt our policy. Thanks Amy, I believe the point is still valid as-is and we followed the no bullshit stuff ;)
I have an IPv6 ISP in Canada (Teksavvy), and quite happy with it (except for the lack of reverse-DNS). I'm too cheap to pay for a static IPv4 netblock at home, but IPv6 works fine to manage the ton of publicly-accessible VMs and other services (wifi mesh network) I run from home.
When I'm working from outside home, I use a tinc VPN to access my IPv6 services, and also redirect my IPv6 traffic through my home network.
Other fun experiment: if you are ipv6-enabled, look at the percentage of bittorrent peers who are in ipv6 vs ipv4. IPv6 is growing.
But still, nice if you want to try it out and test with it.