Build, license or buy their way into an ecosystem. Apple's current formidable strength is its ecosystem of content (app+media) and peripheral of hardware devices (iPhone + iPod touch + iPad + Mac).
Let's make a bold assumption that a Mac counterpart isn't needed. Let's make it even simpler, we'll just need an iPhone+iPad combination of hardware.
Start with a partnership, say HTC with Amazon. So you can have decent hardware for a phone and tablet from HTC, along with content (app+media) from Amazon.
Maybe it's hard to forge such a partnership, maybe there's a dozen of reasons why this isn't possible, maybe HTC like it's current way of business, maybe Amazon is building it's own hardware, but I know I'd want to do this to win.
When you can't win by yourself, partner with someone else so you can win together.