I would continue making waves in the high end walled garden for a few more months. You will have a larger audience in Android, though there will be a lot more

I would continue making waves in the high end walled garden for a few more months. You will have a larger audience in Android, though there will be a lot more competition. Your app is already free, so there will not be a major culture shock moving to Android. Cement your name and gather a strong following. Start work on an Android port but don't rush it. A small amount of dev time to get started, like a day per week, would be enough to start understanding the challenges your team will face in the porting process. It doesn't have to be a major focus at this point, but the early time investment in exploring the next phase would give you a potential to move forward faster when the time is right. Think of it as the hobby project for the business.