The buzz at the Denver Performing Arts Complex is picking up as the Colorado Ballet Company’s 2011–2012 season opener approaches. This year it’s back to the classics, with Swan Lake (October 7–23) followed by the annual rendition of The Nutcracker (last year’s holiday run broke attendance records), but tradition is only part of the lineup: Having just come off its 50th anniversary season, the company has pledged to entertain for another 50 years; look for the latter half of the season to reflect an evolution in artistry, with imaginative, more contemporary premieres meant to reach new audiences.