A sugar cube or 4 with an optical link that links to the ddr ram bridge could be useful in 2 ways.
The increase in layer density and amount of layers could provide better spacing relative to throughput and allow for more capacity in a smaller space or better buffering of dram ram. being connected to an optical to ram bridge on the bus plus a direct connection to GPU RAM across the same bridge does allow for some serious performance boosts. couple this extra capacity of workable ram and storage capacity with optical compute acceleration and state of the art neuromorphic processing plus faster switching and you have eventually a mini PC that can do 8 Petaflops of optical inferencing and 140 Terra flops of parallel calc ability with 2 Peta bytes per sugar cube and 2 Terra bytes of Ram.
verticalizing and making optimal space use is key to this type of future.
I think this is the limit for chips after that the nano scale is more perfected and on top of the thermo optic pin array are very fast optical processors even some quantum computation and the sugar cubes get more nano precise and denser there will probably be a mid array of small fast optical ram down the middle of the to pin array and two sugar cube slots per module which will be like a whole motherboard that connects to a wall array and one room of walls could run the whole of facebook, google, youtube and google earth with ease.