The controllers won't have lighthouse tracking though. The IR tracking is the headset tracking the controller's IR LEDs, which the Index controllers do not have. It might be possible to have the headset IR track the lighthouses, and then use the old Index controllers, which also track the lighthouses.
There's also tools to calibrate the different tracking methods together, but that seems less than ideal.
Good catch, I just saw IR tracking on the page and didn't investigate further. I can't wait to see some teardowns (physical and firmware) of the device, then we can get a better look at what it is truly capable of.
Though it wouldn't help the controllers, perhaps the expansion port on the headset could be used for a lighthouse-compatible tracker? (One can dream...)
There's also tools to calibrate the different tracking methods together, but that seems less than ideal.