I thought Apple were against USB3 in favour of Thunderbolt? If they're not, then why the hell haven't Macs had USB3 up until now? It's been around for at least three years for goodness sake.
...but, until now, it hasn't been built into Intel's mobile chipsets. They'd have had to incorporate a USB3 controller chip on the main board. That's an issue with the smaller MacBooks and it would be unlike Apple to introduce a new interface unless they could rapidly roll it out across most of the range (as happened with Thunderbolt). I also suspect that, if USB3 comes in, FireWire will go out.
I do think Apple are lukewarm on USB3, but now it "comes free" with the Ivy Bridge chipset they'd have to be pretty stubborn not to include it. OTOH I wouldn't bet more than I could afford to use on Apple not being that stubborn!
Thunderbolt isn't really a competitor for USB3 - its more expensive to implement and requires expensive active cabling. I don't ever see people plugging thumb-drives or mice into Thunderbolt. What it
does do is enable forms of expansion which wouldn't be possible with USB3... E.g. the Apple Thunderbolt display with Firewire, GB Ethernet, 3xUSB, sound, webcam and multiple displays all through one wire and performing as if they were on the computer's PCIe bus (you could
attach all those things via USB3, but the USB3 port would be a bottleneck).
However, Apple needs to do something to galvanise the Thunderbolt market - a few very-high-end RAID drives, specialist video add-ons, plus two vapourware docking stations with a miserly selection of ports won't do it.
Prediction: the most common use of Thunderbolt in the next year will be to add USB3 ports to 2011 Macs.