Of course, it is an excellent gift from the developer to include 3D transitions for ordinary spherical panoramas in the new version. The new version 1.21 (and higher) is certainly superior to the previous one, BUT there is a question of compatibility, in syntax, support for old plugins (third-party developers), etc. between 1.20 and 1.21 is a big problem for those who have to some extent formed their established DEV. SET around krpano framework environment. Some people are simply afraid to switch to new functionality for serious projects.
And also, many customers and photographers simply do not need the new advanced 3D functions that are being developed in new versions (3D models, texturing, etc.) THERE IS A HUGE COMMUNITY of ordinary customers who have spherical panoramas and want to create simple beautiful tours WITHOUT stunning 3D possibilities and other things, BUT with some new trends that have long been in demand, in particular this new 3D transition for spherical panoramas. I believe that adding this function to the old 1.20.xx version, which the author himself does not discount, will be a truly beneficial solution. IMO Regards, Gumir. 
klaus.krpano