With that many cores it would not be a case o fthe apps in use today running faster, but rather being able to create apps with more functionality.

Just taking game use, Instead of running AI on one core you could have one core dedicated to the AI of an individual character, with many, many characters in play. You could run several physics threads on several cores with another to manage thread interaction. You could have several cores running ray tracing algorithms to calculate lighting which could then be passed onto the gpu or rendered directly. You could use several cores to process audio streams, decompress and decode textures, video textures etc.

There will not be a case of there being 'enough' processing power for a long time yet, you can always think of more things to do, even if it becomes increasingly difficult to speed up the execution time of an individual thread.