I personally wouldn't bother with SLI or Crossfire since I don't think even much this year it would ever be necessary. As it looks you don't even gain enough with paying the money to run SLI to make it worth it.
I haven't personally ran an SLI or Crossfire setup but based on what i have read multiple places. It's not worth the money.
So in short, it's up to you whether or not you want to buy an SLI ready board or Crossfire for future use. It wont be necessary but if you do you can always brag and say, HEY I HAVE DUAL 7800 GTX's etc