Ah i dont dispute all the above will retain a level of popularity. But regarding affiliate promotions, as “fads” come and go, competition builds and wanes. So my point is that talking about the “next big thing” is really talking short-term in terms of capitalising on revenue making ventures.
It will pay affiliates to keep ahead of the game, but while affiliates are required, there will always be market share available in all these fields, just at varying levels of profitability. A safe bet IMHO is to concentrate on a specific area of interest and ride the down periods waiting for the next wave, unless you have so much traffic that can be cross-fertilised you can afford to change direction on a regular basis.
Cheers
Simmo!