My question is does iOS development
career considered a serious profession
(like Java or .NET)?
In my opinion the carrer in iOS dev isn't serious. You're writing some small apps for a TOY, in most programmer unfriendly enviroment invented, EVER. Look what Apple does to their devs, one time they made illegal developing using some technologies (eg. cross compilers), every app needs to be approved, they made whole programming ecosystems illegal on the device, etc.
If you take iOS dev, you may find yourself unemployed and with nothing one day, because Apple will just ban all your dev tools. That means make all your knowledge illegal to use!
Taking the time it takes to master any technology into account - no this is not serious, very risky. To me it looks like russinan roulette.
Richard Stallman giving a speech at WSIS-2005 => watch the video. You're having preety much freedom with Java and .NET. On iOS - you're an Apple's slave.
If you have some self respect you should choose to develop on some platform that is free, or at least the owner show just a little respect to the devs. Let's face it - you can develop anything you want on Java / .NET and no one will be telling you what you're allowed or disallowed to do based on their humour. Just that makes iOS absolutely 100% not-serious.
Look at Windows Phone, Android. I don't know if that's serious compared to Java but Microsoft/Google will at least treat YOU seriously.