Dealers in the USA are begging for an even bigger LX and have been for 10 years. In the Middle East, LX sells the way it does because it is BOF... and I think it is the best selling Lexus model there. Russia is the same story: high demand because it is BOF, rugged and capable. Lexus has no premium RWD architecture to build an LX on. GA-L is a failure, so a theoretical unibody LX would probably be built on TNGA-K... so... Lexus version of the Highlander = LX? No.
For all of these reasons and more, there is no viable business case for a unibody LX right now, and we know the new LX is coming this year. Maybe next time around once/if Lexus can sort out a competitive, flexible RWD unibody platform? But also, probably not since Toyota is so heavily invested in large BOF vehicles and creating an LX from one of them is a minimal investment, comparatively.
The next gen Sequoia and LX will either be platform-mates or very closely related like the Land Cruiser and LX have historically been. This gives the LX the size and scaleability it needs as it evolves, so breaking it away from the Land Cruiser is actually a good thing. Lexus also has the 3-row TX coming, which will be something like the Lexus version of the Highlander, but that is not an "L" flagship vehicle.
Because GA-L is such a heavy and poorly packaged platform, what we thought LF-1 would be is most likely dead - replaced by what will become the FWD/3 row TX and TBD/midsize/electric RZ. Land Cruiser 300 can continue to sell as a up-spec full size luxury SUV in global markets without the Sequoia.