Macsimumnews publishes an Apple Seminar email which claims "Meet the New Macs" on April 17th. Macsimumnews speculates that this may coincide with new Mac releases at NAB.
The truth, however, is that these seminars run year around with the exact same title.
A quick search reveals other "Meet the New Macs" as soon as March 29th (Thursday). Another "Meet the New Macs" event took place 3 days ago on March 24th (Google Cache).
Apple's seminars refer to all current Macs as "new Macs" and has no relation to product releases