It is very likely that there will be at least one more VSL grand piano sample library in the future beside the upcoming YAMAHA CFX. Please have a look to a post from VSL, which you can find right under their CFX teaser-clip on their facebook-site: https://www.facebook.com/viennasymphoniclibrary/
"Vienna Symphonic Library We like to give you as much choice as possible! Starting with the Yamaha - it is a beautiful instrument and we have seen quite a few piano players who were heavily impressed by the performance (both at Synchron Stage Vienna and in the Synchron Piano Player)."
I personally hope that VSL will sample the new full concert grand piano model from BÖSENDORFER, the 280VC, as this grand is now also available equipped with Enspire PRO like the YAMAHA CFX Enspire PRO, which they already own. And I hope, VSL will publish this second grand within the next year in 2019. I'm sure BÖSENDORFER would be very supportive.
Please have a look at my posts above about YAMAHA Disklavier PRO vs. BÖSENDORFER CEUS.
Their STEINWAY & SONS D-274 is not a reproducing piano and therefore not remotely accessible. Because of this, the recording sessions of this grand with a "human" pianist and editing process afterwards would be much more complicated and therefore much more time consuming. And in my opinion, a sampled STEINWAY D would be redundant to the YAMAHA CFX. If their CFX is a very fine exemplar, then there is no need to have the "same" VI for a second time. A BÖSENDORFER instead would be a really different sound to the YAMAHA.
To have a sample library of a STEINWAY & SONS D-274 satisfies only vanities on the basis of the brand name, in my opinion. Of course, vanities are probably the biggest motivations for buying a STEINWAY. But to make decisions on which grand piano to sample, factors such as abandonment of a pianist, remote controllability, and precisely programmable key stroke gives many advantages through the production. 100 velocity layers in a grand piano sample library - VSL VIENNA IMPERIAL - are not possible with a "human" pianist.