There's going to be a gap made by people who don't port over their software, certainly worth looking at that gap and see if there's something you can provide.

Most software should be just a recompile if it's well packaged. Of course that's a huge if and not everybody wants to support Mac anyway, and I lost a ton of my steam library (not that anybody really plays games on Mac anyway) in just the 32-64 bit transition recently. I also lost textwrangler, which was the greatest Mac text editor ever created and I refuse to pay a subscription for its 64 bit successor.