Ok, ignore the 1200mm. I'm the only one who is wishing for a replacement for that at half the weight.
I have the 200 and 800 that are rumored to be updated next year and I am not inclined to sell then upgrade to the new one unless it offered a weight savings of more than 50%.
It is guaranteed the price of the Series II will skyrocket to beyond $15,000 to make the 600 and shorter white primes look cheap by comparison.
Canon can update the paint job to lower cost by only having to support one color of L white, sharing 1 lens hood for the sake of reducing SKUs and even the lens cap from leather to the more practical canvass.
In the past Canon have made subtle changes to existing lenses that did not merit a Series II monicker. They did this with the 200/1.8.
The changes are the relabeling of the AF switch to "MF" from "M". Optical coating has a different color. An inclusion to a more rounder aperture was made.