There are states in USA and other government bodies, though, that have gone and standardized on the format.
There was an enlightening message thread about the RTF and RTFd format as to who owns it and what it is which surprised me, and I thought, if you save as RTF, that should be readable, so why won't NeoOffice open a file created by Pages 3?
I guess have to do it for myself and 'test' Pages 2 vs 3 to see what happens, and also OpenOffice.org, to see.
Truthfully, I have two files I could open in Numbers (a table of all software program versions and serial numbers), but I don't use Keynote, so Pages for me is the whole $79, and buying Pages 2 last week and 3 this week makes this a $160 word processor 😟