Thanks for everybody weighing in. You know probably how that is when you are going to get new equipment: you constantly think of it until you're done.
I'm ordering on tomorrow or on Monday, but the current state of affair is:
I'll very likely get the 18-55/3,5-4,5 lens as a walk-around and travel lens, and then the 1,4/50, which I am very much looking forward to. (at 1,6 crop factor that's exactly 80mm in 35/full frame: ideal! Of course it is non-IS, but I don't consider this such a problem for portrait/portrait in motion)
The Canon will be good for my desert trips, because if dust gets inside, it's not the inside of a 1000$ lens.
In autumn I expect to get really, really busy, and then I can take a look at more pricey lenses.
What I really think is good: with this line-up I can get up to speed with the new camera, and when September comes, I'll know it inside out. This is why I decided to upgrade earlier: I don't want to get into new equipment in a busy time.
DarkPenguin, the Tamron is very, very tempting. The review at photozone is nothing short of a rave. But I repeatedly read about its poor focusing ability in low light (reviews on the b&h site), and that it's easy to get a bad copy. And it has no IS.
Regarding my wishes, I'd be happy with a 17-70/f4 L with IS for the cropped format. With a magnesium alloy body (no plasticky, dust inhaling stuff) and dust and humidity seals and great optics. I'd prefer f4 to f2,8 for size and weight. But dust seals are a must. I'm in California, and there is dust, dust, dust everywhere... this is why I ruled the 17-55/2.8 out (and its weight was another minus).