It's now been given a release date of 31st July in Japan priced at ¥16,178 ($145) in case you wanted to try and import it. No doubt we'll see a proper Western release soon enough if you wait.
HORI will also be releasing a cheaper alternative to the Switch Pro Controller on the same day priced at ¥3,218 ($29). The catch is it is wired and has no gyro, HD Rumble or NFC reader. It does however have a D-Pad which can be popped off and placed in the back of the controller, presumably so the button arrangement perfectly matches that of the Joy-Con when connected to the Joy-Con grip.
Will you be picking up one of these lovely new controllers from HORI in July?