no thunderbolt on Windows (and no 3.0 on Mac)
That's not quite true at all. Thunderbolt is an Intel technology; Apple was just the first one to support it. Asus, Acer, Sony have already released (or are preparing to release) Thunderbolt support devices. [ArsTechnica link.]
And USB 3.0 could definitely come to Macs at some point. Apple was the company that popularized USB to begin with when they released the original iMac. Now all PCs have it.
For what it's worth, you could make the same case for Thunderbolt. Apple makes it popular, everyone else follows suit.