According to Neowin, HTC sent out an invite on Friday for a mystery launch event on September 15. Since we all now know that WP7 will be coming to Europe in October. And with the recent leaks of HTC Schubert. Its possible we might see HTC officially announcing their Windows Phone 7 lineup.
UPDATE : As one of out reader [ Yinka ] pointed out , this might be an Android Event. via Engadget