SAN FRANCISCO – Apple CEO Tim Cook revealed at a California conference that Apple has sold more than 13 million Apple TV devices – half of those set-top box devices were sold last year. He also hinted Apple may soon offer a wearable computer.

But when pressed for specifics about Apple’s vision for the device, Cook responded bluntly: “I don’t want to answer that.” He then emphasized that he considered the topic closed. “I don’t want to go any further on this – I don’t want to give anyone any ideas that they don’t have,” he said.

Cook was similarly elusive on the topic of wearable computers, calling “profoundly interesting” and an area that was “ripe for exploration.”

“Lots of companies will play in this space,” he said before declining to answer whether Apple would be one of those companies.

But he did have a few nuggets of information to sprinkle on the crowd, including the confirmation that Apple chief design guru Jony Ive has been working on an overhauled iOS and that its APIs could be opened a bit to third parties. And although he declined to offer much insight into the changes afoot, Cook did announce that Apple would be “rolling out the future” of the mobile operating system, as well as OS X, its desktop cousin, at the World Wide Developers Conference in June.