I too do not see a Lexus V8, simply because Lexus does not need any. Mercedes, BMW and VAG have 12 cylinders because well, they can (Maybach, Rolls Royce and Bentley). The V10 engine by VAG is an old engine (2 generations, based on an even older V8). Expect next R8 and Huracan replacement to get current 4.0l V8. Mercedes 4.0l V8 is based on their new generation modular engines and is basically tow I4. V6 is getting replaced by less costly and simpler I6 (I4 +2). BMW has their modular 1.5 I3, 2.0l I4 and 3.0l I6 engines. There were rumors of 4.0l V8 many years ago, but the new M5 will still get the engine based on the already 10 year old 4.4l V8 N63. New M3/M4 will continue with a newer I6, but no significant changes in their performance engines for the next 8 years. No new V8 from BMW, but rather hybridized I4 and I6 engines. Other car manufactures based have their 6 cylinder engines related to V8 rather than I4, thus the 90° angle rather than the 60° angle like Lexus. If Lexus made the V6 and V8 Dynamic Force engines related, they would both be 90°. If Lexus still brings a V8, than we can say they don't cheap out like the Germans and others. FCA 3.0l V6 makes 500 PS, and might come closer to 600 PS in the Ferrari Dino, if it ever comes.
The Land Cruiser's most sold engines that is not an I4 Diesel or V6 gasoline is the V8 Diesel. But this engine is no more sold in Western Europe due to regulations, and we never had any gasoline Land Cruiser 200. The V35A is enough to replace the 1UR, 2UR and 3UR. The replace the 1VD Toyota would have to build a new engine, if a V8 based on an I4. I think it would be cheaper but also simpler and better to utilize the BMW/Mercedes strategy, and simply stretch the 1GD to from 4 to 6 cylinders. It would make more than 300 PS and 700 Nm for the Land Cruiser. It would be a back to source engine, smooth, and "simple", especially as the next Land Cruiser should get IRS.
Although I like V8, I see no need for them. The Germans do not sell a lot of them, even if they earn quite a lot on them. Lexus is simply not as desired as anything German, however good it might be. More than that, V8 turbo does not sound better than the 2Ur, at that point, V6 turbo is fine, same performance, lighter, more compact.
Maybe the LC F will be a V6 TT+Hybrid.