Everything will be run through a huge conversion process to the new system, then leagues will continue where they left off. :)
It's going to be a foundational change to the entire game. With the new design system, everyone will need to re-allocate their performance levels after the update. Plenty more information will be posted about all of this nearer the time. The performance you have will essentially be given to you in the form of points in the new system, and then you will be able to re-allocate it to the areas you want.
As an earlier poster noted, November is probably too soon to expect a public rollout of this update, but we should have a beta online in November and everything in the open for proper scrutiny and feedback. Things are coming together nicely, and just the suggestions we got from the thread and blog have already influenced our direction slightly.
We're more willing to add depth to this first version based on the feedback, and it has resulted in some evolution of the race page already, adding more depth and detail to the setup. In hindsight, maybe we were being too cautious for mobiles and watering it down too much. It's far easier to make something this complex look confusing than it is to make it easy to understand though, so I'm glad we did it this way around, simplifying as much as we can and then layering complexity back in. I feel we are getting close to a perfect balance that will work well across platforms now.