Ad Age is stunned to report that Native Ads are a small part of advertisers budgets. I would suggest that the nature of native ads is that they will remain a small portion of advertiser budgets.
Let me give you an example of native ads in TV: something like Simon Cowell drinking Coca-Cola on American Idol.
How much can an advertiser spend on that stuff? There are limited opportunities, they are harder to identify and figure out, and measuring success tends to be more indirect (although it can be spectacularly effective).