It's still a ways from LEGO Batman's 7m milestone but with boy wizard Harry Potter due again in cinema, it should catch up pretty soon.
Warner made the announcement from their Q2 fiscal report. LEGO Harry Potter only released in June this year so 2.7m isn't bad at all. It's the latest LEGO game release from TT Games the developer of LEGO Star Wars, Indiana Jones and Batman.
LEGO Harry Potter: Years 1-4 released on Xbox 360, PS3 and PC.