Thank you Bob & Felipe for your comments.
I noticed the new version of T-Splines (version 4) but still that does not satisfy my concern about Autodesk stopping or slowing on the updates for T-Splines. If Autodesk Fusion gets good acceptance in the market, there will probably be little interest from Autodesk to continue support for T-Splines.
I tried Clayoo (version 1) and have to say that it is very immature, has too little features and it is too buggy. And, when Clayoo matures well, the price will most likely increase and there could also be the risk of being acquired by another Rhino competitor and treated similarly to T-Splines
I do not want to spend money, but specially time, neither with T-Splines nor with Clayoo.
I started looking into Blender; it is pretty solid, its free, has lots of tools, lots of tutorials, and can do what T-Splines and Clayoo do, and much more. It is not very simple to use, but it works for me. I can export *.obj format and import into Rhino. They are meshes, not NURBS surfaces, but that does not matter. (Clayoo only produces meshes also).
I wonder what is holding McNeel from adding Polygonal and SubD mesh tools into Rhino. Rhino already has limited mesh tools. It would be great if that could be improved.
Thank you again for your help, and if you got this far, thank you for reading my opinion