Just a quick look at the Konova K3 and K5 sliders. Average users won't notice the difference, but the K5 is overall heavier, has a larger inside rail, and larger bearings inside the carrier. So the new upgraded legs with the unusual platform design was something Konova planned several months ago (way back in November). The notched out platform on each end of the new sliders are used for attaching future upgrade kits such as the Crank Pulley system and (not yet released) Motorized Upgrade Kit.
If you don't already have the new legs, you can purchase the upgrade kit from Konova's website. The new legs should also come with the new Carrier stage that is designed to align with the Crank Pulley belt guide (as in the video). If you are planning to upgrade the legs on your slider, you might want to wait until the Crank Pulley system is officially available to see if they might offer some type of 'Upgrade Legs + Crank System Bundle'.
The new Crank Pulley system should be available in a few weeks, and I have no exact pricing yet. Some are saying it might run approximately $150 dollars. [Update] The new Crank and Pulley system is Available Now.