Apple appears poised to unveil a long-rumored headset that will place its users between the virtual and real world. The headset will also serve to test the technology trendsetter’s ability to popularize new-fangled devices after others failed to capture the public’s imagination. The stage is set for the widely anticipated announcement be be made Monday at Apple’s annual developers conference. Apple is also likely discuss other products and software during the event. But the show’s star is expected to be a pair of goggles that could become another milestone in Apple’s lore of releasing game-changing technology, even though the company wasn’t always the first to try its hand at making a particular device.