*** For a monetary unit to be a globally accepted currency it must have PRICE STABILITY! ***
I'm not so sure about that. Have you seen CAD / USD lately?
http://www.xe.com/currencycharts/?from=CAD&to=USD&view=1YConsidering we've got $61+ Billion in circulation here in Canada, I would consider our dollar to be anything but stable. -10% over a year is volatile imho.
Besides, no cryptos are mature yet. Once a crypto is completely mined out (in terms of new blocks of coin), then my best guess is that it would be no more or less stable than the CAD or USD.