Theoretically true since natural selection weeds out weaker competition. What if an organism devolved into something in a new category. That is what could have happened if an organism with a flagellum devolved. It could have turned into something that injected a poison into what it was preying upon.
Can you find a single example of a species that changed into another species by random mutations? That is not what I asked, it was a question asked by biologist Lynn Margulis. She is an evolutionist but not a neo-Darwinist.