I thought about getting Zeiss ZF lenses for my D3/D300. Three or four lenses would give me great range over the two bodies, and they're not as expensive as you would expect. I've hesitated because the reviews I've seen suggest that they're not much better, and sometimes not as good, as the Nikon AF equivalents. I don't believe you could pick out one or the other from a group of photos, although you might be able to see some differences in side-by-side comparisons. Sean Reid discusses some of this on his excellent website; it's not that the Zeisses are bad, it's just that they're not significantly better.
The OP suggests that Sony will have established itself as a major pro alternative by the end of the year. I have to disagree. If Sony works hard at it, perhaps by the end of the next decade.
Why would a pro (or a budding pro) choose an alternative with a much smaller system, unless (and this is the big unknown) the price was so much radically lower that it made up for the other deficits? I don't know Canon (except that it's a good system) but in Nikon, for example, there's an extremely well-developed, very subtle flash system; both Canon and Nikon have extremely well-developed shift lenses; Nikon, like Pentax, has a huge inventory of affordable heritage lenses which provide very different qualities to photographs -- not sharpness, but different drawings; if you're at a big event, with a Canon or Nikon system, there's always a possibility of borrowing a lens or two if you have an equipment problem. Not so easy if you're the only guy there with a Sony. Because of this, if I were a budding pro, I'd simply go with the established systems (except for the possibility of a radically lower price.) You really can't go wrong with Canon or Nikon - why mess with Sony?
I say this not so much because I'm a Nikon guy, but because I bought into the Kodak DSLRs -- they were expensive cameras backed by the biggest name in photography, and they are now gone. That thought is always tucked away in the back of my head.