Some future Intel processors are to have 6 cores in a single socket. I believe they'll be compatible with socket1366.
Knowing that most dual-socket boards were (are?) extremely bad on graphics, and very expensive, it could be better to await (2010 Q1?) this six-core instead. And then, don't buy the mobo until you know it works with the Cpu.
Windows 7 gives licences for a number of sockets, so check it against the version of Windows you plan to buy - this as well may get expensive.