Firaxis know their strategy games, and it's already been in development for 3 1/2 years, but kept tightly under wraps.
Every single interview I've seen gives the impression that the staff at Firaxis have nothing but the utmost respect for the old X-Com games, and want this game to be an improvement and expansion upon the old formula, not just a rehash or a cash-in… So I think fans of the old games can finally afford themselves a little optimism. :)