Are general relationships between MTOW and OEW valid for novel configurations?
Many studies and presentations you will encounter about radically different configurations with much higher performance are the aviation equivalent of car commercials. Someone tries to get attention in order to get published, or she/he needs to convince investors to fork over their money.

Trust me, the aircraft designers of the last century were no idiots. They had the luck of living in a time when it took only a few years for aircraft designs to become obsolete, so they could go through the whole design process many times and apply what they had learned before.

Someone graduating from university today will be lucky if she/he gets the chance to go through every step of a major design process even once. I myself have brought three aircraft into the air and consider myself very lucky. I had colleagues who retired without ever having seen one of their many projects take off (literally).

The consequence of this is a very mature industry which has found an optimum configuration for most purposes already and is only tinkering with the details. Add to this an ever increasing thicket of regulations which have grown on the experience from existing designs. Sure, the progress in computer control is impressive, and engines get better all the time. Manufacturing precision is ever increasing, and materials still become better and more consistent. But overall, we still build aircraft like we did a generation ago, and I do not expect this to change radically in the future.

What impacts the design process most is certainly the incredible precision of simulation software, which allows to see details which remained hidden in a wind tunnel or a strength test. Things which had to be done consecutively can now be done in parallel, and the precision of knowledge at an early stage of a design is much higher than before. But at the same time aircraft become ever more complex, so the advantage of better simulation is eaten up by the increase in complexity. Add to that the fact that mostly beancounters will have the last word, where before engineers could determine how the work was done, and you will understand that the level of preparatory work is shockingly inadequate in modern aircraft companies. Many of the avoidable early mistakes will require late, expensive fixes (but by that time the stingy beancounter has left the company with a huge bonus for the money he bragged to have saved).

The design process is still the same, and where before the experience of a few people helped to find an overall optimum, large, integrated teams will together determine this optimum. The inexperience of the participants will only show up in delays, when the iterative design cycle needs to be repeated more often than anticipated, but the result will be of high quality - really bad designs are a thing of the past. But cutting corners will still have consequences, so small annoyances will still plague new designs. Consequently, most of the engineering work will involve ironing out these annoyances or retrofitting new systems to existing airframes.

To answer your specific question: Yes, the relation between OEW and MTOW will still hold in the future, and radically new configurations will show an advantage only on paper, before they have been thoroughly designed and test-flown. Better materials and methodologies will help to improve the ratio between OEW and MTOW, but this advantage risks to be eaten up by the desire to add bells and whistles everywhere.