The British Computer Society published a list of grand challenges for computing. Unfortunately, for many of them it will be hard to tell when we've accomplished the challenge.
The Free Lunch is Over: A Fundamental Turn Toward Concurrency in Software describes why we are unlikely to see higher clockspeeds and other simple scaling soon, so that performance increases in software will have to come from concurrency to exploit multicore processors, with a bit of assist from larger caches. 64-bit processors may actually decrease application performance.