I've been giving Bitcoin mining a lot of thought for a few months. I couldn't find a good description of why the current generation ASICs will be so much faster than previous ones or where things might go next so I wrote an article about it (perhaps I've missed one though, in which case I'd appreciate any pointers).
Hope this might be of interest to other people:
http://hashingit.com/9-where-next-for-bitcoin-mining-asics