Basic tenet of security. Enable what you use, disable what you don't.
Every unnecessary function you enable adds potential vulnerability's.
IPv6 evangelists aside, the need for IPv6 is dubious at best. For me at least it is absolutely unnecessary.
It's less efficient than ipv4. It's more complex than ipv4. ipv6 tunneled over IPv4 is the worst of both worlds.
It offers as its justification "universal connectivity".
That is simply an alternative statement of "universal vulnerability".
Worse it builds in auto configuration. So if some device on the network tries to bypass the blocks that exist to limit "universal vulnerability" the ipv6 functions will actively assist in bypassing those blocks.
On ipv4 those "features" are add-ons to the protocol and can be disabled.
How long will v6 be supported?
Oh boy...
Most of your post is simply wrong, the other parts are not wrong because they just don't make sense.
How long will IPv6 be supported? It is built/made to be used between colonized planets.. It is/was designed to replace IPv4.
IPv6 is more efficient than IPv4, not less. More complex? How so?
IPv4 can be thought of as just an experiment, it worked, so everybody said, "it is working, don't touch it".. IPv6 was thought over, discussed, and debated by multiple committees for a long time..
I used to do that, just disable IPv6 in any system I interacted with, but that is just a crutch.. Every "issue" you have with IPv6, already has a solution, every annoyance is there for a good reason.
The biggest security issue with IPv6 is that if you are not using it, turning it off on your routers for example, that it becomes easy to setup a MITM router on your LAN to capture lots of traffic.
All OS's default and prefer IPv6 over IPv4.. If you have an office of people accessing a mainframe using telnet, a network device can advertise IPv6 addresses and an IPv6 address for the mainframe's FQDN, workstations will automatically start using and prefer it.. All it has to do is then forward the traffic to the IPv4 address and nobody would notice for a period of time. Especially *you* on the router, ignoring any/all IPv6 traffic.
If you had setup IPv6, you would have the tools and knowedge to notice.
IPv6 isn't going away, IPv4 is. I strongly suggest you learn it.
The time to voice your complaints and suggestions for IPv6 has long past (20+ years ago).. A speak-now-or-forever-hold-your-peace situation.. It was published in 1996 and updated in 1998.. I don't agree with all (just one actually) the updates/changes done in 1998, but that is my opinion.