There's a lot of variety on your gallery... although you mentioned a variety of brands (which each have their unique strengths, weaknesses, etc.) I think you should stick to either Canon or Nikon to get the broadest, most flexible product line at a reasonable cost. Unless, of course, you have either a very strong set of reasons -- artistic, creative, niche interest, or other -- to start up on another system, or a very large budget.
Keep us posted on what you choose to buy! Always good for all of us to learn from the thought processes in this kind of a decision.
Forgot to mention: there is some gorgeous work on your gallery, Joe... went there to see what you shot to see what I could suggest in terms of gear, and ended up spending a bit of time browsing. Very nice.
Thanks much Rodolfo. I have spent much time learning to make pretty pictures and have made some progress in that regard. And much of it was with committed focus and dedication. When the early retirement option came along, and options for pursuing the Master degree, well, I got excited, and my family did too and offered encouragement. I will be learning to raise the level of my work, learning more about photography, and ending up teaching photography at a College/University.
Needless to say, I am thrilled to be able to give making pictures my complete attention.
Since I made that decision, met with professors, etc, and engaged in the application process, several clients have contacted me about doing some work.
Gees, I will be busy now! And doing what I am supposed to be doing hopefully, even at my age.