IPv6 compatibility?

The biggest mistake in developing IPV6 is it lacks backward compatibility with the existing IPV4. IPV4 was made standard protocol 13 years ago and still it is the standard protocol. I also studied these both protocols in my computer networks course apart from articles i studied on net and in books, and there were some ways shown to make IPV4 devices compatible with IPV6, but there is no effective technique yet to make IPV4 devices compatible with IPV6 or vice versa, IPV6 developers envisioned a scenario in which IPV6 and IPV4 devices and networks will work side by side,which is known as dual stack mode. But they failed to realize that some IPV4 devices will never be upgraded to work with IPV6, and IPV6 networks have to communicate with IPV4 devices.. i hope that IETF will come up with some idea to use IPV4 and IPV6 side by side as it is impossible to change the devices and networks overnight to IPV6 from IPV4