Basically: Ruby + Cocoa will not rely on bridges in the future… LLVM’s Compile-time optimization will almost certainly translate to iPhone development once mature, even if JIT is not made available for system performance reasons (which is dubious given it’s great performance levels and increasing iPhone hardware).

Re: cross-platform (beyond OSX/OSXmobile), this is definitely important for MANY tiers of developers.
I honestly think things are looking good from Apple’s end of things, assuming they follow thru on MacRuby (extending the approach to a MacPython would be even better).
…So I don’t know if the problem is really on the MacRuby side of things, or if it’s equally/more a question of “language independent .NET development” working as promised…?

I’m not sure if you’re already aware, but if you need more motivations to be happy about working in XCode, you may want to check out:
http://www.brandonwalkin.com/bwtoolkit/