Your last motherboard has lasted 5 years or so, meaning that it isn't neccesary to upgrade every socket.
I see your point, but as CPU designs change and new chipsets / features are added I don't see how one motherboard to accomodate new technology without a major redesign - i.e. making them modular.
Perhaps that is a good idea, you buy a base motherboard with VRMs etc and then upgrade it in modules as and when needed. However, this is probably more expensive and less practical than the current system.
Haswell is still a year away - possibly more - so I do not see the point in waiting, especially when Ivy / Sandy users can happily sit out that socket as even if it is a massive leap forward there is no guarentee that games / software will even be using all of the grunt available currently at that point.
I fully expect to keep my Ivy build for a long time.
I've put off upgrading for some time now, I plan to get a 660 when they are released and don't want the rest of the system bottlenecking, so it's on the cards, just wanted to see where the future is heading and it seems closed roads are likely and it's been that way IMO since the 775.
I think what will happen is I'll pick up a 2500k and decide on a mobo, any suggestions on the chipset, it's mainly for gaming, though sli is not important.