A Workable Definition of SF (For Now)

Given that we can't really discuss science fiction thoroughly without a working definition for it, I'd like your opinions on whether or not the following is a definition we can use for the time being:

"Fiction that speculates on future societies and future technology (in the near or far future) or on on things such as space travel, government, human evolution, robotics, aliens, technological advancements, etc (or both). It is the genre that asks 'what if?'"

One concern, obviously, is whether we consider works written long ago that no longer are considered 'relevant' as far as the science is concerned to be SF. I would posit that we have to still consider them SF because we must look at when they were written and the fact that, at the time, they were SF. 1984, obviously, is off by quite a few years, but we still consider it SF. The same can be said about a lot early SF.