Phones & Tablets
Surely the best way to engage today's youngsters in programming would be to focus on development of apps for phones and tablets? I'm sure the idea of creating their own app for their phone would have a lot of appeal, and for many students would be more relevant than, for example, playing with the naked electronics of a Pi.
A coordinated programme as was set up with the BBC micro is also an important part, but the goals should still engage the students. Add the fact that the tablet paradigm is almost certain to replace the current desktop paradigm by the time today's kids leave school, it would keep teaching as up to date as possible.
Currently, to program Android, you need to learn a fairly complex IDE (Eclipse) running on a standard PC - either Windows or Linux. That's in addition to learning Java itself! I wonder if a stripped down Eclipse running on a dedicated build of Linux as a kind-of "development appliance" is feasible? You'd still need cheap PCs to run it on, but they would just be the means to an end.