I am following outerra since years, and the improvements in the views are HUGE since the very begining.
Your big work and our big waiting time totally worth.
But for me the more important things your engine need now is a more accurate source in terms of terrain data and colour data.
Actually Outerra use 500 m pics for colors, this is great for the begining of the NON monotone world as before was, but still is a lack in the color richness the world should have.
In the same way, i see the 90 meter terrain resolution as a begining of your tech, but also still a lack in terms of terrrain accuracy.
Improving this in a (lets say) 100 m pic resolution and 30 m terrain data would mean anther BIG jump in how outerra looks.
Imaging this working together with your tools (probably improved in the future), fractal terrain detail, customizable trees system, biomes, roads, etc.. Practically, any user would be able to reproduce their real place in this virtual world with high detail and accuracy.
And more if we talk about the future tools, if you ad for example fractal modifications based in geo maps.
So i can see all the advantages, and would be big. Also you can think in the posibilitie of put the high definition version for the pay version and keep the old for free. This can also be the push some people would need for support the proyect.
Also for posible developers interested in buy the engine would be a very good thing see outerra being so accurate in world definition. Basically any developer interested in simulation would have all the base for begin. DOnt doubt the future simulators based in your amazing engine will have high resolution data (i remember myself playing fsx with certain places in 5 m terrain data and 1 m real texture back in 2005 and we are in 2014).
Its true as you said, anteworld actually is just a demo for show the tech. But i dont think this make a high resolution version pointless. It would be the oportunity to show all the tech potential to everybody, also the demos are for that.
And seeing also at the cons. Yes, more space, more time for download. Maybe add some server. But for me the advantages would be much more than the cons (they would look like a minor problem, because Basically, nothing would improve the outerra views more in just one step than that change). Because all is adaptable. We can just wait a bit more to download new places, we can create torrents dividing the world in continets for download too, some more server can be added, etc.
I think even if you are about to create rivers, lakes, and road system, would be better to do in a base of high res, so you will not need to rework it in the future. Because you are already working in the future. (lets say you decide not to improve datasets in 2015, in 2 years you will do and needing to rework all probably).
This is my humble point of view.
Keep the great work.