There are reports that the Montreal Expos, who have been relocated to Washington, DC, are to become the Washington Nationals. I believe that was the original name of the Washington Senators, who are now the Minnesota Twins. (The other Washington Senators are now the Texas Rangers, by the way.) I've heard that this will all be announced on Monday, along with displaying the new uniforms and everything.
Personally, I'd like to see something kept, if altered slightly. During their entire tenure as the Montreal Expos (from 1969 to last year), the team has used this logo:
It's sort of a stylized "M". The small red "E" in the lower left-hand corner stands for "Expos", while the right side of the logo (the blue) is a "B" which stands for "baseball". Thus, "Montreal Expos baseball".
I hope that, when they reveal the logo for the new team, it looks like this: