I agree with Marks on this one. The key here is that VPS requires dedicated servers. Thus the more popular VPS becomes, the more specs will be needed, and the more powerful the VPS packages must become. This in turn means that the dedicated servers used to power VPS must become more spec intensive, and as such become more expensive.
While the average consumer may not continue to utilize dedicated servers over VPS, VPS still requires dedicated servers. As the internet grows, and moves forward with the demand of more power, and more specifications, servers will need to increase in power and specs. As long as the internet is here, the need for servers will never disappear, but instead increase.