As I said, it may be confusing, to have many diferent versions of a same theme. But it can be usefull too, to see how autors evolve, and how their themes evolve...yes, it may be interesting.
And if the last version of the theme is well "marked" (ie. a bid fluorecent and shining logo "last version"...lol...), the confusing may be reduced.
But there is still one more PB, the theme names. You see, I name most of my themes "themename" (without version number), so if i try to upload an updated version, I can not do it without giving it either a diferent name, either a versoin number.