I just read about a new 100-400L on www.canonrumors.com
No more push-pull and now with a mfd of just 31 cm, it will be great for bugs, crawlies and birds.
It also has a new IS system promising 4 stops.
US pricing will be around US $2200, so not too bad for an all new L lens.
I love my older version, but if the newer version is noticeably better, my old one will be on the market.