RockShox have just started teasing the release of a new fork via their Facebook page. Details are slim at the moment, but the given images clearly hint at an upside-down design. The slim profiles in the images make us believe that this fork is designed to be light-weight; but it's designation remains unknown.
Update 22/03/2014: RockShox has released an image of the complete fork.
Update 22/03/2014: RockShox has just released a further image depicting the bottom of the fork including the axle.The thru-axle appears to be the 'Maxle Lite' - which was released for the 2014 season. Upside-down forks (aka inverted) need a solid axle connection for stiffness, the fact that a hub has been pictured could be a way of hiding a new axle design or perhaps even a new standard.
The RS-1 naming hasn't been seen since RockShox's first fork – released in 1989. Stay tuned for more...