Illustrative Programming will fit particularly well with, and benefit from, programs that collect, crunch, and display data - this being area that I agree will see a lot of growth and attention.[2] "The ability to take data—to be able to understand it, to process it, to extract value from it, to visualize it, to communicate it—that’s going to be a hugely important skill in the next decades,"[3]
Tools that are more suitable for large and complex data sets than Excel, and easier to use than R will become available. These will be used, as many current programming languages are, by people that are not trained in software development. Visualization will become much more important, so programming tool usability will improve. We'll see the influence of statisticians in our programming tools. Chasing down posts by others with similar problems and bugs will become easier. I'm not sure how much headway Illustrative Programming will make into the more hackerish areas of programming, though I hope it's a fair bit. For the best predictions on what languages will be like, just look critically at the languages that are at the start of their lifespans now (http://mythryl.org/ ? Arc?) and also at current research.
I think, though, that the most interesting changes will come from the sort of programs we'll be writing, the sort of people we'll be working with, and the sort of tools we'll have available, rather than from some feature x or y of some future major language.
[1] http://martinfowler.com/bliki/IllustrativeProgramming.html [2] http://flowingdata.com/2009/06/04/rise-of-the-data-scientist... [3] http://flowingdata.com/2009/02/25/googles-chief-economist-ha...