After three years of closely guarding his strategy for Apple Inc., Chief Executive Tim Cook will show his hand Tuesday, with an ambitious blitz of new products and services that aim to resolve questions about the company's ability to innovate.

Apple is expected to unveil two new iPhones with larger screens, its first wearable device—a smartwatch—accompanied by new services around healthcare, home automation and digital payments. It's the type of new-product wave that Apple fans have been waiting for since Mr. Cook succeeded...