My prediction is the product line will be streamlined from 4 to 3 laptops to offset the tablet product line growing
MacBook 12 - casual user 5W TDP
MacBook Pro 14 - pro user 15W TDP iGPU
MacBook Pro 16 - pro user 28W TDP dGPU
You can fit 14" and 16" 16:10 screens in the current MBP 13" and 15" chassis quite comfortably judging by the screen/chassis proportions of the 12" MacBook
That is assuming they have not been working on a bezel-less screen to compete with Dell, if they have then they can do 14" and 16" AND make the chassis smaller. I don't think the chassis needs to be smaller in width/depth, just thinner.
The MacBook Pro 16 may be released in September, so they have more time to test and optimize for the new Polaris GPU .. so it would be a staggered release
Late april - no event MacBook 12 refresh (newer core M CPUs, 1 more port, price drop)
June - MacBook Pro 14"
September event - MacBook Pro 16"