What kinds of programming languages may be developed and used in the future?

It is always very hard to predict the future, especially in an area which has seen very rapid development over the past two decades.

In software engineering of applications interfacing with human users, powerful new declarative approaches are the modern choice, such as Microsoft's Windows Presentation Framework (WPF) and its XAML language, or Adobe's Flex (with MXML), and others.

It is probably fair to assume that the declarative part of application design will grow in the near and mid-term future, taking even more responsibility for the mundane tasks related to graphical user interface development off the programmer. This allows to focus more implementing the application's core algorithm and logic.

It's probably also fair to assume that the dividing line between desktop applications, web applications and mobile applications continue to diminish both in term of design as well as in terms of usability: applications will increasingly work within a web browser, and it will be common to have a (possibly feature reduced) mobile app on a smart phone or tablet computer, or a desktop app all resulting from the same development effort.

It is fair to assume that programming languages will continue supporting this goal in even more comprehensive hardware abstractions and increased automation of the housekeeping work.