E-beam is more mature than optical for sure. But electrons, primary, photo-, or secondary, are prone to random disturbance. And they go into the substrate. So the interest in DSA, though it seems sensitive to the guiding pattern size.
The dream of e-beam direct write has been around as long as x-ray lithography, and just as successful. The e-beam problems of throughput, data management and error correction simply cannot be solved in time, or economically. EUV, or, more correctly, soft x-ray projection lithography, continues to suffer from very x-ray like problems of decades ago. The only technology with the potential to complement optical lithography is imprint, which essentially is optical lithography: it uses an I-line source, I-line resists, and quartz based photomasks. Defects are a more manageable challenge than those facing EBDW and SXPL (EUV), particularly in memory. Lithography will bifurcate into solutions for logic and solutions for memory.
Perhaps, regarding as the viewpoint of mass-production, the approach to improve the common DOF of the different characteristics of pattern,ex. iso- vs. dense- ,or line vs. space, is more practical and economic than that to put all resource to enhance the resolution.