Couple things:
1) There is no such thing as an early announcement with Tesla. Elon Musk is the anti-Steve Jobs. If he has something on his mind or Tesla has a plan, Elon Musk will tell the world through his Twitter account or if he is in front of a microphone. There is a long, long history of this. My personal favorite is at the 2013 All Things Digital conference when Walter Mossberg asked Elon Musk what the big Super Charging announcement would be. Elon's response, "I shouldn't ruin the surprise but,...."
10 Things You Missed From Days One and Two of D11 - Eric Johnson - D11 - AllThingsD "Tesla Motors CEO Elon Musk announced
— one day early — that the company plans to triple the coverage area of its faster electric car Superchargers by the end of June, and release a car in the $30,000-$35,000 range within “three to four years.”
2) Again, back to the speculation game, I believe Tesla (and Panasonic) are going to move fast on this giga factory. Think NUMMI. Tesla acquired NUMMI in October 2010. Less than two years later, Tesla completely retools NUMMI with machinery from Detroit that Tower Automotive could never operate and starts to manufacture 100% electric vehicles. This giga factory will be operational in less than two years. I believe they are recruiting a Gilbert Passin equivalent to run it. And like Toyota did with NUMMI, Panasonic will be able to help out with location and most likely a pre-existing structure.
I agree with Bonnie, Tesla probably wanted to announce this yesterday.