It seems that at least a pair of plugins have been developed for this:
http://dev.pathtoenlightenment.net/shop/currency-switcher-woocommerce/
and
11/27/15 Deadlink: http://codecanyon.net/item/woocommerce-currency-converter/4545063
I couldn’t vouch for either as I haven’t used either. I think that some multisite extensions are also in development, which might allow different sub-sites to show the same product in different currencies/prices.