Unfortunately, I don't think Canon will release anything in the 'affordable' 400mm range just yet. It's all over all the forums...people have been crying out for one of these to get upgraded for years, and one might suspect that Canon knows about this...they could make a real killing if they were to release an updated 100-400, 400/5.6 IS or 300/4...yet there is no sign if one.
Don't know about sports, but for wildlife, especially smaller critters, one needs all the reach one can get, and even 480mm (300 on crop) won't be enough. This is why those less expensive 400mm lenses are so important for wildlife photography (and, in addition to affordability, weight is another important factor, both for hiking and hand-holding without the need to bring a tripod too).
The 100-400, the 400/5.6 and the 300/4 + TC are, at the moment, the only Canon lenses that will get you there on a budget, and they are all very old designs, all in need of an upgrade.
The 70-300L announcement was quite a disappointment to those anxiously waiting for one of these.
Of course, there are third-party alternatives, but for fast and reliable AF and IS you still need to go to Canon.
I don't see myself paying 4000 euros or more for a 300/2.8 or other super-zoom unless I win the lottery but I would be prepared to pay well into the 2000's (Euro) for a new 100-400 4.5-5.6, with twist zoom, updated coatings and IS...Come on Canon, my money is waiting for you!