Apple heads into next week's Worldwide Developers Conference with its stock near record highs, iPhone momentum improving and one unresolved question hanging over Tim Cook' s final developer conference as CEO: Can Apple finally deliver the artificial intelligence experience it promised two years ago? The expected centerpiece of WWDC is a major overhaul of Siri , Apple’s long-criticized voice assistant. Analysts expect Apple to show a more powerful version of Siri with a standalone chatbot-style