The issue is that the bar is low for an IRC client on a handheld device... which means competing for "a good product" isn't really a useful thing to do. A "good" IRC client on a handheld is just something with an input box, channel buffer, optional nicklist and a displaying of channel events. Multiple server/channels included, of course. A pretty UI would be icing on the cake. There are lots of apps that can compete in that field. There is nothing really special about doing any of those things. Everything that makes mIRC special would be gone, so the competition would be who could best market their "buffer window with an input box", which is probably just a crapshoot. I can't confirm this with certitude, but it seems to me that the reason Khaled still enjoys working on mIRC is because he is producing something that is truly not being duplicated by anybody else. I don't think he is really interested in writing an IRC client "just 'cause", or reinventing the wheel. It's hard to innovate in a space where the only user requirements are: "connect to server(s), join channel(s), send text, receive text".
And I'd echo what The_JD said about a port not really being "mIRC" at all. I could swear there was another thread on this topic very recently where I basically said the same thing, but I can't find it right now.
