These days x64 is widely supported.
For a communications program being able to communicate with the whole world with the least effort(over 7 billion people alone, not counting the all kinds of devices) is more then a must.
Proper IPv6 support e.g.
There are already various free 64-bit IRC programs, either solely irc based or with the functionality in it.
There are free ways to compile a 64-bit program.
Using 64-bit programs for some time now, a well written 64-bit program has more then speed advantage.

Best regards to Khaled from an early mIRC'er

mIRC already supports IPv6; that's unrelated to a 64-bit version of mIRC.

There is nothing inherently faster about a 64-bit program than a 32-bit one unless you're specifically dealing with 64-bit values as a matter of routine, which mIRC does not.

Most 64-bit benchmarks show that 64bit applications only have speed benefits when dealing with large amounts of data-- we're talking over 2gb. For small data, which would be the overwhelming case for an IRC client, the performance boost is basically non existent, and I've seen benchmarks where the overhead of 64bit was actually a detriment (though not really significant) to speed. This is to say that there is little evidence to support the "speed advantage" assumption.

This isn’t really a future suggestion. It’s inevitable that mIRC will eventually start offering a 64-bit version. Since mIRC is compiled via visual studio, it can already be compiled in 64-bit mode. That being said, there are no real merits to accelerate this process. IPv6 is already supported and as for the speed boost, mIRC will probably perform faster on 32-bit anyway. This due to the fact that most operations are done on small buffers (due to many inherit limits like line/irc/vars/etc), moving to 64-bit will probably hinder performance a little (not too much) due to the fact that on-chip cache will be exhausted quicker. Of course only a profiler could validate that assumption.

I have been using mIRC in Linux via wine. This will become more difficult in the future because popular Linux distros like Ubuntu and Redhat are starting to phase out support for 32-bit architectures and binaries. I would like to continue using mIRC without having to resort to making my user environment too customized.

Are there any plans to make mIRC available as a 64-bit binary?

Khaled has been working on a 64bit version.

The latest beta (7.57.669):