I've known at least one person (and possibly more, it's hard to remember...) who went for a MD after years as a nurse, a couple who went on to nurse-practitioner or PA, and one or two who have shuffled between RN and EMT-P positions as pay and adventure dictate. If you spend some years as a nurse and decide later that you want more schooling, you'll be experienced regarding the options available and probably in a more financially stable position. If you continue to yearn for academia, there are a both teaching and research avenues out there in the nursing and nurse-practitioner fields.