Since I was bored I decided to make some completely unscientific projections in Excel:
NV and AMD dots are the peak GFlop/s ratings of their top end cards (I've omitted those gens where there were no top end chips like AMD's Polaris).
MS and Sony dots are peak GFlop/s ratings of 360/XBO/XBX and PS3/4/Pro respectively.
Now this gives us some range to work with, and I'd say that 16-18 TFlops for a console launching in 2020 is highly unlikely - we're looking at ~10 TFlops being the sweet spot in this time frame - twice the throughput of XBX tops. To launch a 16 TFlops console they'll probably have to wait till the end of 2022 - which is kinda confirmed by the PC top end GPUs Flops projection which stays roughly 2,5 times ahead of console GPUs.