I wonder, does the fact that Microsoft has retained the "Pro" designation with its latest announcement mean that there might be a new "Surface" tablet/2-in-1 in the future?  

I doubt it. Most likely Microsoft is leaving the low-end 2-in-1 market to their hardware partners. On one hand, the Surface 3 continues to serve well and I don't foresee a near future where a new release of Windows 10 does not work on it. On the other hand, it makes me think further about what device to buy next. Right now I basically have a tablet for work,  the Surface 3, and a tablet for home, the iPad Mini 4. Both are orphans and why do I need two?