My humble opinion: if you think along the lines of MSX2 or MSXturboR, and especially if you hear this story, for me it becomes even clearer, that if you would want to extrapolate what was commercially released to MSX3, it would be an MSXturboR with a V9990 (it's the closest actually released silicon to what you have to the unfinished V9978). The OPL4 also makes sense, as it is/was a follow up to the OPL chips that were part of the standard.
So, to me, if we speak about MSX3, the most logical thing is MSXturboR with V9990 and OPL4. Ideally, to make this combination more like what would/may have been the V9978, the V9958 of the turboR should be superimposed on the V9990. This is the only missing thing, at least not something easy to get.
OK, that's my dreaming 
The fact that Mr Nishi rejects V9990 is more like a personal thing, I think, as is pretty clear from his story. And yeah, I understand that it reminds him of some bitter times that he'd rather forget.
I agree 100%. And he is confirming to us that the V9990 is MSX related. And I'm happy that the MSX community has embraced this VDP (since 1994!). It is nice to see, at last, 16-bit era games running on our machines. Kai's Metal Dragon port to Megadrive/Genesis has shown how good the V9990 is. Both versions are almost identical (well, the MSX one uses more colours on screen at once ):
Metal Dragon MSX
Metal Dragon Megadrive/Genesis
And the game even runs at an acceptable speed on a bare bone Z80 MSX2 (yes, 8-bit computer with a Z80 3,58MHz CPU and only 64kB of RAM): Metal Dragon MSX (Z80).
I think the people reacting so negative on Nichi’s statements are biased themselves.
They probably spend time/money buying v9990 and/or developing the hardware/software.
But Nishi is right..MSX Turbo-R is the latest official MSX standard until now and is the baseline to develop further on.
V9990 is just an expansion cartridge like SCC. Popular but not part of the MSX standard.
Spending his limited resources adding complexity by adding a 30 years old VDP that was never part of the official MSX standard is just very unwise.
So Mr. Nishi has my full support! (Worth nothing but still )
Whether or not the v9990 is official or not, it was quite needed, and is still needed I'd say. It solves a lot of things that are annoying and difficult to do with MSX2. It's just that no-one's using it. It's like people who keep voting for the wrong politicians and then complain they get bad politics. 