The trend of niche-languages (e.g. Objective-C for iPhone) isn't actually a new trend. For example the high performance computing (HPC) community uses Fortran nearly exclusively for decades. The number of niches increases, though, so i expect further diversification of languages. E.g. game development is not C++/C# only. Most games include at least a scripting language (Lua, Python, Javascript) and many feature some online league, which may be implemented with typical web languages (Java,PHP,Python,Ruby,...)
In terms of programming language features i expect the next hot topics to be:
Dependent types, however, the question, whether a type system should be turing-complete is not answered yet.
Optional types for dynamically typed languages. Common Lisp had this for centuries of course, but now Python introduced the syntax and Clojure etc. also support this.
Various mixes of concurrency related concepts. There are lots of ideas currently (see X10, Clojure, Go, D, Haskell, ...), but no sweet spot is found yet.