The upcoming RTS I'm most excited about is definitely Supreme Commander, the 'spiritual sequel' to Total Annihilation. The game has a real
sense of scale, and includes units from infantry to tanks to strategic bombers to battleships to aircraft carriers, all sized appropriately and on a humongous map. It relies more on true simulation (for instance, calculating the actual trajectory of a cannon shell to determine whether or not it hits a moving target) than rock-paper-scissors relationships. It's also elimenated a number of micromanagement issues by allowing you to appoint a computerized commander to monitor your base while you concentrate on the strategy.
Unfortunately, the official website
doesn't have much at this point.