I’m a Swedish nurse so I’m not sure that my opinion and experience is applicable on bedside nursing in the US. Here entry-level for nursing is a BSN. In 2010 47% of all nurses had attained a MSN. Masters degrees are available in surgical care, medical care, oncology, pediatrics, nurse midwife, geriatrics, OR, intensive care, anesthesia, prehospital (ambulance), psychiatry and district/community nursing.
Five out of these are a requirement to work in the various specialties (nurse midwife, anesthesia, intensive care, OR and prehospital) and will result in an increase in wage. The other specialty MSNs are not required for employmeny in that specialty but gives the nurse a competitive edge. Whether they will lead to an increase in wage or not varies. As a general rule two years of full-time clinical experience as a BSN nurse is required before starting a MSN program. (Exceptions have been made for future OR nurses since we’ve experienced a shortage in that specialty).
I don’t know what a MSN in the US entails. Here a MSN typically consists of clinicals in your chosen field, a more advanced level of knowledge (compared to the BSN) of the relevant pathophysiology and pharmacology, and more (again compared to the BSN) evidence-based practice and research methodology. The BSN is broad/generalist and the MSN is specialist/niche. All of which I consider a real asset bed-side and in my opinion in no way makes the nurse overqualified.
Again, I’m not sure if my opinions are helpful to you. There are many aspects to consider. Here, higher education is free of charge so the financial burden for the student/nurse is lower. But as you say in your post, you believe that further education will broaden your knowledge and keep yourself marketable. I agree with that. Also, who knows what the future will bring. You are happy bedside for now. Should you ever change your mind you will have more career options available to you with a MSN. So if you have the time, motivation and financial means to do this, I would say “go for it”!