My years working on black programs
During the Iraq War, everyone marveled at the great new technology behind the Predator drone to conduct surveillance and deliver ordnance during strike operations. Then it leaked that the Predator had been developed 15 years earlier and used successfully in Desert Storm. Cut to 2011 when we learned that the SEAL team that killed Osama Bin Laden used a stealth helicopter, something that no one in the world had any public success toward achieving, and we not only achieved it but were running classified missions with it.Based on those two examples alone, I estimate that the most secretive programs are 15 years more technologically advanced than we are in the public domain.AI and Quantum Computing come to mind as likely focus areas in addition to those already mentioned.