It's nice to have cross platform ability with BlitzMax but I am afraid after a while it'll all end up on a Windows platform.
This is almost certain *not* to happen -- Mark is a confirmed Mac-head now. He's not going to drop support for his own preferred platform!
Remember that only the supporting stuff has to be written for each platform, most of which is now in place. Since the actual modules are mostly written in Max, Mark only has to recompile them on the other platforms -- "instant porting" rules!