The MetaTrader 5 platform update will be released on February 17, 2017. The update will feature the following changes:
The update will be available through the LiveUpdate system.
I don't think they have any plans to implement this. The only chance of this happening is if the Market refuses to move from MT4 to MT5 in 3/5 years time.
Microsoft finally have emulators to run X86 apps on ARM chips, but it took a complete fail of their Phone and tablet businesses before they delivered a solution, and they waited over 5 years too.
Since Metaquotes currently have the largest market share and don't have competitors like Android and iOS I suspect they won't need to implement MT4 emulation on MT5.
But no one can stop you dreaming