Low-cost tablets like the Google (GOOG) Nexus 7 and Samsung’s (005930) upcoming 7-inch slate are expected to drive tablet shipments to a record 145 million units this year. The estimate comes from ABI Research analyst Jeff Orr, who says increasing enterprise interest will be another catalyst for tablets in 2013. Orr also believes Windows-based tablets will begin to gain steam this year and that North America will remain the world’s top tablet market, responsible for over 50% of global tablet shipments in 2013.