Adwords will remain a popular advertising tool for a long time to come. high cost of keywords will keep force some advertisers to shift to YSM etc. PPA (pay-per-action) will play a much bigger role in the future. http://adwords.google.com/support/bin/topic.py?topic=11635
Hold on, let me check my crystal ball... It says that the future is uncertain. Hmm, sounds more like the response from a magic 8-ball. Anyway, I think Google is here to stay for probably another decade at least. They are keeping on top of all of the latest trends (and even starting some of them) which is what it takes to remain in that position.