I'm going to put my two bobs in, for what its worth
I reckon that port is a eSATA port, too. This makes sense considering the target market - people that will use such a port. I know, because I've got a MBP and a WD hard drive with an eSATA port, but I can't be stuffed getting an ExpressCard adapter for eSATA.
And eSATA is currently the fastest external connection for things like hard drives - at 3Gb/s. Video editing through one of those would be wild.
Seems a bit odd, though, they'd get rid of FireWire on the MB. I can see them using the 4-pin connector, rather than the chunkier 6-pin connector. But, to be completely honest, what devices does the average consumer use that uses FireWire? Digital camcorders? Nope, they all now use USB, except for the MiniDV tape ones. iPods? Haven't for ages, and for those still using the old ones - if you're upgrading your laptop, why the hell not your iPod?! Hard drives? Firewire is really only a benefit when you're using FW800, and hardly any drives have that, most have USB.
Consider, then, the number of devices that use USB. It makes much more sense to place an emphasis on USB, rather than Firewire.
As for HDMI, I know of one device that is
SCREAMING out for a HDMI connection - the Mac Mini. Just think - why would you want HDMI - to connect to a TV. What Mac is perfectly suited to connecting to a TV? The Mac Mini. A TV Tuner, HDMI and a Blu-Ray drive in a Mac Mini and they'd sell millions.