I hope they don't either to be honest. I can see where you're coming from aswell as far as earth's significance goes, but its the home of Humanity, which happened to be the thing you set out to save in ME2. You can tell the other races are going to get involved too, so it might be interesting to see war on earth with people like the Asari etc.
Either way, Bioware are going to pull us in one way or another. I can't wait to get on to Earth aswell. As the trailer shows (and living in London my entire life, it was expecially awesome for me.) There are landmarks are around, and it will be cool to see a future version of the Earth we have now, rather than what looks like some random earth colony.