Forget about the redesign for 2020
Next year we will have probably the 14”, and 13” will remain for the macbook air for those who wants the ultimate mac portability
Probably next year only the imac could see a slightly redesign
The ARM will begin for non pro macs, like macbook air or entry level imac or mac mini
Pretty much the most sensible way to go. Which professional wants an ARM based MBP which has support for so few of the frameworks they use? Will the brew package manager even work for its release? How about the tens of thousands of packages that people rely on? How bout the stability of every non-apple developed app, like Chrome, Adobe, etc. ARM conversion is no small undertaking. The most likely route is Apple will create an 'arm-branch' of their laptop line and most of their software, and it will take years for all other developers and Apple themselves to get it to the place where intel support is at.
In terms of hardware, you are dreaming if you think there is another redesign coming. Think about this- Tim cook walks into a room and says, great job everyone, people are loving the new MBP 16. Now, please go and design a new version that wastes all the effort ($$$) and time ($$$) we sunk into this one. If even there was one already in development - its likely to be pushed back now if nobody has any major complaints. Tim Cook is all about optimization and what you are suggesting is just about the most suboptimal action there is. And even if this unlikely scenario were to play out, as others have pointed out, there is very few new tech that could constitute a redesign cpu bump, maybe faceid, thats about it.