No iPad 5 Until Mid 2013
Going by my gut instincts and business background, I believe that the new iPad or iPad 5 will not be announced Early (March) 2013 rather it will be announced Mid Year or fall of 2013. First off, Apple has usually stuck to the almost one year cycle for products (except for the ipad 4). The only reason the ipad 4 broke the mold was because of the lightning adapter. Apple needed to have all their products running with lightning or people would not care for the ipad. The reason they updated the internals was for extra sales. If they had updated it and left the specs the same, consumers would demand a price decrease because technically the ipad 3 is slower than the iphone 5. Apple can not stand to have a budget ipad with similar prices to the mini and ipad 2.
As for the iPad 5, the announcement cannot happen this march, mainly due to manufacturing and shipping. As i recall iPad mini and even iPad 2/3 chasis were leaked months before actual release. As apple becomes larger as a company it will be harder to keep these products secret. If apple was to announce and launch a new ipad in march we should have some case mockups already. Because if apple plans on selling 10 million of these within one quarter they should have already started manufacturing. Im sure the next iPad will have the same internals as the iPad 4. Partly due to manufacturing costs, and partly because it would be cheaper to manufacture. Using the A6X with an igzo display will reduce battery size and weight, which will reduce the overall size of the ipad. The A7 announce will happen in fall of 2013 with the new iphone.