The next step in computer architecture is to get rid of the Von-Neumann architecture. We are at the limits of it. Intel and AMD have skirted the issue by adding more cores but even that has a maximum theoretical limit. Speeds cannot be increased much over 3Ghz due to power consumption and power fall off above that.
I've read that bio computers may not be a bad solution but I strongly feel that Quantum computers are vaporware and will most likely not be ready for quite some time, if ever.
