I see; in this model, Homo sapiens becomes the name of a shared ancestor of both modern humans and Neanderthal. Where does H. rhodesiensis fit in this model? Or do would they be the initial sub-species of H. sapiens? (Wiki notes that they are sometimes termed H. sapiens rhodesiensis.)
This kinda gets at a question that floats around my mind. How different are we, from the prospective of an outsider, to
Homo heidelbergensis or
Homo rhodesiensis or any other hominid fossil from the last million years? Certainly, to us they look... different. But is their morphology as different from us as the three species of zebra? My suspicion is no. It is for that reason that I would lean towards considering them all
homo sapiens... and it's also why trying to label species, I think, is somewhat of a silly endeavour.
But to get back to your question, I'm not sure where to place any specific fossil in relation to our ancestors. Trying to label any as a human ancestor is guess work. I'm not too concerned with knowing just which fossilized example was our direct ancestor. It's enough to get the idea of what the ancestor would have been like. It's for this reason that I lean towards calling
Homo heidelbergensis or
Homo rhodesiensis as just archaic, or if pushed to give a precise name, include them as subspecies to
Homo sapiens.
If you want a hard answer, ask a paleontologist. If you don't like the answer you get from him or her, ask any other paleontologist for a totally different answer.
Also, out of interest, exactly how far is the label "human" understood to extend? Is it simply to Homo sapiens sapiens, to all homo sapiens or to the entire genus? I assume that it doesn't extent to non-homo hominids, at least not unless we implicitly include chimps.
Another question that will yield you completely different answers based on whom you ask! I would lean towards what I said earlier about silly endeavours. The variation found in modern humans (between mental retardation and those with minds beyond my comprehension) is going to be larger than the average person today and our ancestor 500,000 years ago.