As I said in my last reply Microsoft can extend support for Windows 10 for as long as they wish. For all we know now Windows 10 could still be developed in 2025 so support would be extended for 10+ years after that date. The same type of extensions were done several times with Windows XP.
So the announced lifecycle is for the circumstances known at this date and is subject to change. i.e. Microsoft has not released any information about any possible new OS's that might be under development which could replace Windows 10.
Rob - SpiritX