The L3 memory integration was recently hinted by a series of 01.org test results checking for L3 cache hits/misses on an upcoming Snow Ridge ULV chip. Snow Ridge and Lakefield are both codenames for next gen Atom CPU families expected to launch in late 2019. These will integrate the new Foveros 3D packaging for hybrid architectures that combine desktop-grade cores with ULV ones.
https://www.notebookcheck.net/Intel-s-next-gen-Atom-CPUs-may-integrate-L3-cache-memory.427688.0.html