32 bit Microcontoler

BeagleBoard?

I believe the Arduino served its purpose brilliantly. To create a platform to start using electronics. It is then, the responsibility of whoever wants to deepen their knowledge to find on their findings and pursuit of knowledge.
Plus, every day, I get amazed at how much the Arduino is stretched with the applications built by people with very little knowledge of electronics... so I think it is safe to assume that if they manage to create such things, moving on to different platforms should be a step they would take easily.

Plus, a huge speed with an 8 bit microcontroller wouldn't be that good... and there are plenty of platforms to develop on with 32 bits. You've already got hooked into electronics, now it's time you put some more effort into it. :\