I would like to known if and when UNISA will be phasing out BTech degrees in Engineering as I know many other institutions are? I would also please like to know if I could start a BTech in Mechanical Engineering halfway through the year in semester 2 of 2019 or only 1st semester in 2020?
The first part of your question which deals with when Mechanical engineering is going to phase out, we would say per our sources and understanding it is not anytime soon. So you can apply when ready.
As to whether to apply in second semester or in 2020, it depends largely on you. Second semester application date starts from 6th to 13th May 2019.