They have been talking about doing things with heirlooms that would eliminate the need for mailing them to alts altogether. My guess is that they're still trying to figure out the best way to handle it internally. I'm 99% certain that we'll be seeing cross-realm heirlooms before this beta is over, just wait and see.
---------- Post added 2012-05-10 at 11:40 PM ----------
Except that this system is actually being implemented as we speak. They're patching the servers with it right now.