What happens when your core competency becomes your "core liability"? And how realistic is virtualization on a mobile device? Seemingly, Apple and Google have

What happens when your core competency becomes your "core liability"? And how realistic is virtualization on a mobile device? Seemingly, Apple and Google have created a large barrier to entry by making compelling mobile environments (aside from the nuances of each). If your developing for both of those platforms, then why would you develop for another?