I'm curious, do any HN ios developers worry about the future of being an iOS dev? The conventional wisdom with programming is that no programming language is s

I'm curious, do any HN ios developers worry about the future of being an iOS dev? The conventional wisdom with programming is that no programming language is safe, and it's wise to branch out and keep learning. I'm pretty deep into ios now, and looking to embark on a new challenge. What should I learn next? Haskell? Rails? Node? Android?