Yes, there is great advantage to the new connector. It will allow faster data transfer but that's not the important part. The port itself will be smaller, when you're talking about the real estate of something like a phone, size does matter most.They're also moving the headphone jack to the bottom where it belongs.
Well, it's a good thing then. But I wonder why they didn't do this in the last version (4 and 4S). It doesn't look like new technology was leveraged, just a revised design.
I would applaud Apple if they do provide an adapter so that it can work with older accessories.
It probably wasn't ready for the 4 and to change it for just a relative simple upgrade with the 4s makes little sense when you can do it theoretically with a new design of the iPhone 5.
Apple will supply an adapter, you will just have to pay for it.