Workflow as such looks merely a personal task management solution, rather than an enterprise grade BPM system. As such, the fact of its acquisition by Apple hardly changes much in BPM landscape and may look even not directly related to BPM topic.
However, on a wider scale, it has clear and wide going implications to BPM in general. It clearly illustrates that BPM techniques and approaches quickly turn from a specialized narrow field of corporate management into a mainstream technology. BPM becomes an indispensable part of both corporate and end user consumer segments, so that every large player in IT field considers mandatory owning or acquiring this type of service.
One may assume that this acquisition is just one of many upcoming events and marks a new wave of BPM growth moving it into primary application stack, along with standard office tools found on every workplace or private device. No doubt, it will trigger many new startups and development in BPM field.