Mathematically, given enough time, its possible that all species will eventually die out due to enough mutations OR given enough time it is possible that species can change into higher forms. I believe the former to be true, based upon what we know. I think ToE leans toward the latter.
Need to make a slight correction there. It is not change into "higher forms", it is just change.
If we go back far enough, back when life first showed up here on the Earth, it was just single celled (or maybe even less complex than that). At that point the only possible direction life could go was towards more complex critters. But once more complex critters existed evolution was not always towards greater complexity and it was never towards "higher forms".
There is no directionality in evolution beyond what works just good enough. There is no goal other than living long enough to propagate. There is no "higher form" or "lower form", no "more evolved" or "less evolved".
Anyone so limited that they can only spell a word one way is severely handicapped!