eSATA has already been around for a while and as far as I understand, it can connect external drives to a system without converting to USB first.

Perhaps somebody could explain why USB3 would be better than eSATA?

Finally, when can we expect the bright future promised by Intel Light Peak? This is one of those technologies that Intel is developing that really impresses me and makes me consider Intel the Bell Labs of our time.

Erm, USB3 has been show every bit as good as promised already in devices, and who the hell still uses PCI? But you are right that even PCI-E single lane slots have a little trouble providing full bandwidth to all ports at the same time on some of the expansion cards that go with single-lane.
But even so in practise it works like expected.

Do they even make old PCI versions? Can't image to be honest.

Time will tell how much better USB 3.0 will be to the current 2.0 standard. From my reading online, adding a PCI card isn't always going to get you the added speed due to the PCI bus slowing things down (compared to a native 3.0 connection on the motherboard). Also, forget the 'claimed' speeds of USB 2.0 and 3.0. I'll wait for the real-world comparisons to see how good 3.0 is going to be. In any event, it'll be faster than 2.0 out of the box and faster in time with updated driver support and so on.