Forum Moderators: open
SEO - As long as there are search engines their will be some form of SEO. Algorithms will continue to filter the results that human editors don't have the time to monitor, thus there will always be some form of optimization.
PPC - Again will always be around as long as there are advertisers willing to spend money. Especially with the last 12 months growth. I think PPC engine will soon be forced to account for click fraud to some extent with Google leading the way.
Banners - see above
Email Marketing - Our company does all the above, with this (Email marketing) being the only source on a steady decline. With end-users getting smarter and smarter, and spam more and more in the fore-front, email marketers will rely more on opt-in programs. Of course then you have to consider pay-per-view marketing.