This is probably what they meant:
"Developers will move, I believe, from monolithic frameworks like Angular.js and Ember to a ‘pick n mix’ of small, dedicated libraries to mitigate the risk of churn"
Source: http://www.breck-mckye.com/blog/2014/12/the-state-of-javascr...
For every project and team, you [and the team] have the flexibility to choose the libraries that would be effective for said project. Thus, the ad-hoc framework would generally be different for every project.
In general, you [or the team] probably wouldn't re-invent the wheel, and you'll likely to find a decent library on npm.
Take this basic idea of what an app does (I use code in this context to mean js that was written by you.)
Input -> The code -> Output
Frameworks: The code exists in all three areas, resulting in having to change all three areas of the code instead of one.
Libraries: The code exists separate of the input and output, allowing one to make changes to any of the three areas without having to change much (if anything) in the way the code works. This (in theory and usually in practice) also makes testing easier to develop even if the code wasn't designed with testing in mind.