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.
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.
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.
Truly a shame that more 'professionals' don't look more seriously at e-beam lithography themselves, and not take the word of people in the photomask industry, who would directly be threatened if mask-less lithography came into popularity. E-beam litho has demonstrated nano-level capability for more than 20 years, with comparative overlay capability equaling the best aligners out there. Yes, throughput is an issue, but at 1/6 (or less) the cost of an good immersion stepper, you can buy several!!! Truth is that even the finest nano-imprint tool or EUV stepper will require masks, and they will only be available via e-beam lithography (as well as being ridiculously expensive and short lived). Direct write is a viable technology - today!