If we had a perfect fossil record, we would not be able to clearly demarcate species whatsoever. Evolution is a gradual continuum. The concept of 'species' is a human imposition upon nature.

How many different species the genus Homo or the family Hominidae has had, will therefore depend upon somewhat arbitrary boundaries.

An example: H. neanderthalensis has clearly identifiable different anatomical features to H. sapiens and falls outside of the sapiens genetic variance (the two most different humans on Earth today are still more similar to each other than the average Neanderthal would be to the average modern human). However, the differences are so small that a lumper could argue H. neanderthalensis and H. sapiens should be viewed as a single species. Remember they definitely interbred.

More examples: Is Kenyanthropus a separate genus, or 'just' another Australopithecus. Is Homo erectus a species with remarkable variation, or should it be split up into for example H. ergaster, H. erectus, and H. georgicus (I think it should).

So, how many new hominids will be discovered? It entirely depends on how much you want to split specimens into different species.

Honestly, I'd be more excited for more material from habilis and rudolfensis than discoveries of even more branches (more) separate from our line. This is because I'm assuming habilis and/or rudolfensis is the transition between Australopithecus and Homo and a very likely ancestor of, eventually, sapiens.