YouTuber's GDDR6 memory upgrade confirms NVIDIA indeed had plans for an RTX 2070 with 16 GB VRAM
NVIDIA GeForce GPUs are now in the Ampere generation (with availability issues still plaguing them, of course), but Turing cards aren't fully outdated yet and are quite capable of effectively driving today's AAA titles. The RTX 2070 and its Super variant based on the TU106 GPU come with 8 GB of GDDR6 memory, but it looks like NVIDIA did have plans to launch a 16 GB version back then.
Evidence for this comes from YouTuber VIK-on, who posted a video showing replacement of the Micron 8 GB modules with Samsung 16 GB ones on his Palit RTX 2070 card. He seems to have got this idea from leaked NVIDIA PCB schematics that indicated support for both Micron 8 GB and Samsung 16 GB modules. Though the diagrams actually correspond to a PG160 board, VIK-on could try it on the Palit RTX 2070's PG180 board as well.
The modification seemed pretty straightforward with VIK-on only having to remove the Micron memory and replacing them with Samsung GDDR6 VRAM, which he seems to have purchased from AliExpress for about US$200. One major tweak that was needed was to change the resistors for the RAMCFG jumpers to correspond to the binary values for the Samsung modules.
On boot-up, the RTX 2070's BIOS was found to be compatible with the new Samsung 16 GB modules. GPU-Z also seems to have recognized the the new memory correctly. While VIK-on could run 3DMark Time Spy with a score of 6,176 points in the Graphics test, the clocks were all over the place and the card crashed when it hit 1,965 MHz while running a FurMark stress test. Besides, the Time Spy Graphics score is quite less considering an average of 8,952 points for normal RTX 2070 cards.
Nevertheless, the experiment can be considered reasonably successful as it could boot into Windows 10 without issues. The lower benchmark scores and instability could be due to the soldering or some VBIOS compatibility issue with the Samsung 16 GB modules.
Watch VIK-on's video below (in Russian) to know more about the process.