whether its a new socket, Faster Ram or a new interface feature like PCIe, or SLI, theres always going to be something new coming out in a few months.
If you're still on socket 478 then you're obviously not the type to upgrade frequently, so I wouldn't worry about a socket change. By the time you are ready for another major upgrade, you will still end up needing a new mobo + ram along with the processor anyway. If you need/want a pc now get it. Waiting won't give you any advantage for future upgrades.
If you were the type to upgrade frequently, like once a year, you might want to keep a closer eye on upcoming changes, since waiting a few weeks might allow you to reuse more components, but if you only upgrade every 3-4 years, there isn't much use in waiting since odds are the majority of your system will be obsolete by then.