The details are all kinds of sparse, but T-Mobile is sending ’round e-mails to let everyone know to keep the 21st free. They’re going to be announcing something in NYC in just under 2 weeks – but what could it be?

All sorts of things! It could be the grand unveiling long-awaited acknowledgment of the Sidekick 2009 – or might they be making the HTC Magic’s stateside journey official? Will the Android Cupcake build work its way into the announcement? Maybe they’ll blow our minds with a new $120 per year digital picture frame? The possibilities are endless. Okay, fine – maybe not endless. Maybe there are more like 3. Still, excitement!