Given that this is more based on Pokémon designs, rather than the games alone (this affects the merchandise, anime, manga, and so on also!), I'm going to ship this one over to Pokémon General. Hopefully Brendino & Adventure don't mind too much!
To answer the topic at hand however, I was reading an interview with Satoshi Tajiri recently. He stated that hundreds of designs got put forward for Pokémon X&Y, but so many of them were turned down. So I don't think that they're running out of ideas, but their concepts (or at least the ones that get through) are a lot more abstract. They're certainly getting more creative, and less basic. I think people struggle with the fact that because their ideas have to be based on more "exotic" creatures and so forth, that compared to Generation 1, Pokémon are becoming less familiar for us. Whereas in the beginning we had Pokémon based on cats and dogs (Meowth, Growlithe), The Pokémon Company don't want to continue to base Pokémon on animals that have already been used as references. This led to them looking outside the box and basing things on more mythical creatures, for example if you look at Yveltal, it's most likely based on a Hræsvelgr, but it would be boring if we had yet another dog styled Pokémon, right? Their ideas are not running out, as I say, but they're certainly getting more abstruse and diverse.
