In theory, they could, but it would be a terrible business decision. Their whole business is software. Even if they didn't have their own mobile OS and had no p

In theory, they could, but it would be a terrible business decision. Their whole business is software. Even if they didn't have their own mobile OS and had no plans to ever create one, creating an Android phone would make them into a hardware company, competing in hardware with a bunch of other hardware companies that have much more experience in being hardware companies than they do. Since they do have a mobile OS, I can't think of a better way to destroy any possibility of that OS ever succeeding than for the company making it to market a phone running their competitiors' OS. If even Microsoft doesn't believe in their own OS enough to make only devices using it, then why should anybody else?