I'm not saying that it's a good idea to get rid of the ethernet port. But they removed it from the air, and if they really want to make the MBP thinner, then it will have to go.
The next MBP is expected to have USB 3.0, since it's natively supported by the Ivy Bridge CPUs. So the speed wouldn't be a problem, unless they only give us one 3.0 port and you want to use it for an external HD.
I could see them removing it from the macbook pro, but I don't think there is any way it will disappear from the mini any time soon. Ethernet ports make a lot more sense on desktops anyway and the laptop people will be able to get it via thunderbolt if they want to.
I've been to places where WiFi is not an option, I definitely need ethernet. The MBP is thin enough, making it thinner won't squeeze it anywhere it couldn't go before. No need to remove any ports and achieve nothing.
MBP is a pro machine. Wouldn't make any sense to sacrifice performance for space, not to mention there isn't muh more you can save out of removing the Ethernet port. If I want to save space, I would have gone for an Air instead.