Over Facebook this afternoon, SRAM leaked a new rear derailleur they have been working on that bears resemblance to the traditional X.0 unit with a revised front section. While many were wondering if this was hydraulic or just a new design, it appears this new rear derailleur from SRAM is looking to compete with the XTR Shadow Plus from Shimano.
So what do these derailleurs do?
The ideal is to have a clutch mechanism inside the derailleur body that actually increases spring tension to tighten the chainline and prevent noisy chain slap. This would allow for longer rear derailleurs that are required for 3x and large 2x setups to get similar features as short cage derailleurs while drastically decreasing the noise the noise your drivetrain makes while riding. They also keep the chain from jumping gears over really rough terrain due to the increased chainline tension.
On the Shimano XTR unit, there is a switch that takes the derailleur from normal to firm. On this close-up shot, we do not see anything that looks like a switch, so this might be an always on option. However, SRAM has not given any further information about this new rear derailleur other than the linked pictures…so this is all speculation at this point.