Here it is a wish-list with features and ideas to improve the library. Note that features listed here are quite high-level and could be long term additions for the library. Current version of raylib is complete and functional but there is a lot of room for improvement.
raylib source code has some TODO marks around code with pending things to review and improve. Also, check GitHub Issues for further details!
raylib 2.x
raylib 2.5
raylib 2.0
raylib 1.8
raylib 1.7
raylib 1.6
raylib 1.5
raylib 1.4