Retaining the current chassis would distinguish Land Cruiser from other Toyota trucks and SUVs which, to my understanding, will share a new platform. For purposes of distinguishing Land Cruiser for its robustness and durability, this would make sense.
Despite its robust mechanicals, the 200 in both forms (luxury, and extreme luxury) is a marketing failure. Neither Toyota nor Lexus have moved more than 5000 units in the U.S. market in years.
Returning to Land Cruiser's heritage of straightforward capability, reliability and durability makes a lot of sense.