Antoine's along the right path.
These pics are of a next-gen Miata chassis test mule taken at the old Nurburgring track in Germany (there's a new Nurburgring next door where the F1 cars currently race, but this is the original track). Many manufacturers (BMW, Porsche, Mercedes-Benz, even Cadillac), use this track to test suspension tuning - this is what Mazda was testing with this test mule.
As such, the bodypanels have nothing to do with what the final product will look like (basically they just put some sort of shell there to do their chassis testing with).
The next-gen Miata will debut at one of the '05 autoshows - don't know which one yet, but from what I know, here are the candidates (in order of likelihood): Geneva, Chicago, Detroit