This subject is really pulling the feather out. We have no idea how the supply will match the demand, and that is the largest affect on the retained value.
The first year, sure it may be possible to sell a new Elio higher than purchased, so long as EM can't keep up.
Now after things balance out in a couple of years, well, we still have no solid idea. The Geo metro has swung way up and way down as various factors come to play, much more so than other types of used vehicles. So I'll guess the Elio is equally or more affected by those same issues.
All you can bet on, is while Elio supplies most of the demand, used Elios will sell for less than new. And while Elio's remain useful to us, they will cost as much as the need demands.
So if an Elio has a reasonable reliability factor, they will be floated up by the usefulness and pushed down by alternatives such as buying a new one, or other used car. That's where there is a possible difference to traditional market pressures. The low price compares very well to the usefulness for a huge population of commuters. So the price will be at least slightly higher than traditional depreciation can predict, ... unless Elio over supplies greatly.