This is probably a stupid question, but I don't know the answer.

Will older versions of mIRC still "generally" work when IPv6 is in place? Or will I be forced to upgrade?

I don't believe any IPv4 internet software will work with a pure IPv6 environment where no IPv4 emulation is available. That includes this current version of mIRC, since it is still IPv4 dependant.

I don't believe you have to work for many years yet. There are still people successfully using Windows 3.1 even today.

- Raccoon