It's funny - I've read two completely counter reports over the last 2 weeks.
The second is this, obviously, but the first was one of the mags (autocar, autoexpress?) phoning Ford who said the next gen Mondeo would be based on the new Focus platform etc etc (so would likely be a very decent steer).
I'll believe something when there's an official word. Until then it's all rumours.
The current focus is massive, no doubt the new one will be bigger still, so makes sense to just do a better job of saloon / estate versions of that to take the mondeo market without having to make an entirely different platform for two ranges very similar in size when the typical 'mondeo' size market is constantly being diluted with all the other niche models.
The other thing is that pics and info of the MY19 Mondeo facelift are all over the web. It'll get the 8 speed auto from the Focus, the newer twin scroll turbo engine (that the US Fusion already has), external tweaks etc etc. There are pics everywhere.