After an initial delay, Hearthstone has officially started Test Season 2. This means the next time you log in to Blizzard's online card game, your rank will have been reset, but the game will have improved.
The transition happened during today's scheduled maintenance periods in all regions - so it should be live everywhere except Europe, at time of writing:
Along with the bad ranking news for current players, there's more bad news if you didn't get around to opting in for Hearthston beta access. Blizzard has announced that it will not be accepting any more opt-in accounts for beta access - and will only be sending out invitations to those who have already signed up.
This invite wave has not yet happened, as we are still compiling the full list of accounts to be flagged. Once the accounts are flagged, the Hearthstone license should show up in Battle.net Account Management.
No idea on timeframe for this (or when Hearthstone will officially launch), but for now, if you're lucky enough to be in the beta, hop to it!