The best place to get an answer to this, if not from a Linguistics prof, is a career advisor at the university you are considering. Maybe look at the skill specifications of any current Linguistic jobs being advertised.
Your BA and MSc won't disadvantage you if you then have a PhD in Linguistics. But it also sounds like you aren't sure which path you want for your career and if that comes through during an interview you could be passed over for someone who presents as very committed and can give a good answer to the 'where do you see yourself in 5/10 years' question.