The only way it is going to be solved is by more people working on it. As the world's largest engine manufacturer, you can bet that Honda has been working on it for a long time, and that they have some clues about the issues.
But the reality is this - so long as a car can go 100-120k without issues, it is past any warranty timeframes, and people start to soften expectations.
I'm fairly confident that even today's DI can do that. Add a port injector like Toyota does - don't even need to run it 100% of the time, and deposits could likely be very minor.
The best way to solve these issues is to invest in the knowledge to do so, and Honda is a good manufacturer to be getting real world data on it.