I disagree, as a professional developer who has worked with several large corporations..
The elephant in the industry is that the app world is dying.. Perhaps like a bubble.
Heres why: There are hundreds of screen resolutions, os versions, and devices in general. Each one of these hurdles creates a new hardship for a developer. With the induction of CSS3 and HTML5, developers are able to create cost efficient solutions that support multiple devices. (Responsive Design). This helps eliminate waste of financial resources and time while increasing productivity. This also allows a developer to make modifications to the app without requiring a user to download an update.
You will find that now that most apps are simply a wrapper for a website that cache an offline version. Now while i may be discounting the app world, I understand that there is still a need for it with certain criteria such as games.
My recommendation is to focus on CSS3, HTML5, PHP, & MySQL unless you are trying to develop a game or an app that doesn't require an internet connection. An app developed using web technologies can still be submitted to the app store with a wrapper.