All of the languages mentioned above have enough of critical mass behind them to succeed and even flourish in the future. The right answer for you will depend more on the nature of your business and the structure of your data than on whether one platform becomes cooler than yours.
Toward that end, here are 10 principles that will guide the evolution of scripting languages in the future. None of these will offer the definitive answer and save you from a long evening of dessert, liquid refreshment, and debate, but they will provide some guidance that may make the answer appear with more clarity.
1. The semantic barriers won't be as important as the languages rush to steal good ideas from one and other. The dynamic languages are blurring together faster than they're distinguishing themselves.
2. Frameworks are becoming even more dominant. Some people identify themselves as Django developers even though they're writing Python code. Ruby has been around for years, but it didn't become a rock star until it was matched with the Rails framework.
The right solution may require you to choose both a platform and the framework itself -- time to plan another evening of discussion.
3. Applications are becoming their own worlds. There are 23 job listings for WordPress developers. While the WordPress plug-ins will be written in PHP, the programmers will rely heavily on the standard set of libraries included in WordPress. Is it fair to say that the coders are working in PHP, or are they really working in WordPress?