As we gear up for the launch "in beta", we should prepare a nice sitenotice that explains what's going on.
I've put up a quick draft here: https://meta.wikimedia.org/wiki/Wikivoyage/Beta_notice
Would appreciate edits and translations. The "oldwikivoyagelink" will be replaced via JavaScript as that's more reliable than using magicwords in a sitenotice.
Cheers, Erik