I don't think Apple will announce before August/September. Apple ALWAYS announces when their devices are ready to ship (White iPhone aside...)
Apple will go bankrupt before they announce a product and wait 2-3 months and let the competition catch up. I see too often companies like HTC, Samsung, and Motorola announce a product and wait 2-4 months til release. By then the competition caught up and game over.
Apple will either announce June and release June/July or announce August/September and release around the same time.