#####I suppose that I'm only assuming that Earth history will go on, so I guess I am only making an assumption that dogkind would evolve into something seriously different given enough time.#####
It would seem to me that the two things (earth history going on; "x" evolving into "y") are mutually exclusive. Not to mention that we have observed earth's time passing, but have yet to observe a dog evolving into something else.
#####Since Creationists have no described mechanism to their "species boundary" theory, then I will further assume that it is (to quote Dataman) "just a guess".#####
You're free, of course, to assume that it's just a guess that there are species boundaries, but dog breeders, chicken farmers, and many others have been crashing into those barriers for years. You seem to be saying, though, that barriers observed daily are "just a guess", but an assumption that those barriers could be breached, though such a thing has never been observed, is to be taken as a given.
So if a dog breeder can't do something, it is impossible in principle? I never knew of an omnipotent dog breeder.