Since the Nats moved to DC in 2005, the O's average rank in attendance has been 20.7 and averaged 2.1 million fans. They have constantly beat out 8 teams in attendance (TB, KC, Mia/Fla, Pit, Cin, Clev, Oak and CWS). In the same time have beat all but 7 teams (NYY, Bos, StL, CHC, LAA, LAD and SF) in at least 1 season of attendance.
The Balt. Metro area has a population of 2.8 million. This doesn't count an a city like Frederick (who is included in the DC metro area) but is an O's stronghold.
Charlotte metro: 2.5
San Antonio metro: 2.5
Portland metro: 2.4
Vegas metro: 2.2
Austin metro: 2.1
Indy metro: 2.0
Nashville metro: 1.9
Memphis metro: 1.3
I say that to say this, If the O's are relocated, it'd be a crime. Constantly outdrawing (or drawing as well as) 10 other MLB teams or relocating the team to a metro area with a lesser population because of Angelos' brothers incompetent ownership or Manfred's pettiness.