If you're a web designer or developer, the next frontier for your freelance business is iOS/Android development. Whether or not you feel like you're prepared to tackle the creation and coding of apps, iOS/Android development will become increasingly important in the coming years.
While you can teach yourself how to make tomorrow's next big thing, you can also learn iOS/Android development through free online courses. There are also schools and certification programs that will teach you everything you need to know to shift your career from basic front end web design to iOS/Android development.
If you've downloaded an app in the last several years, you've probably wondered how the graphics, interface, and functionality all work together on the mobile platform. It's difficult, and sometimes can be more difficult than back or front end coding. But iOS/Android development is an imminently learnable skill, and you're not alone in your desire to learn it. Consider joining a Meetup group from Meetup.Com to discuss your current career as a web designer, and how you can morph into the field of iOS/Android development.
One of the easiest ways to do this is incrementally, if you're not going to create a community around it or go back to school. You can watch videos, do short practice tasks, or make "dummy apps" that will never be available on the app store. This is all a part of your iOS/Android development portfolio, and when you start looking for jobs in the field, you can look back on these projects as your first and most important steps.
If you think you want to be a part of the next big thing in mobile apps, iOS/Android development should be your next career goal. It's hard to learn, but with discipline, training, and a good attitude, you'll be coding in no time!