The correct answer was
1991, for the Toyota 299T program aka 1995 Toyota Avalon (XX10). Design freeze of the 1995 Avalon, was completed by February 1992, as evidenced by these photos from a February 17, 1992 patent filing, that was registered in April 1995 with JPO. This design above was 299T Program Proposal
B (1991), which lost out to the winning choice.
XX10 Avalon Design Patent Images, Filing Dated February 17, 1992
299T Program Design Freeze of XX10 - January 1992
Here is Proposal A as well:
299T Program Design Proposal A 1991-Toyota Headquarters, Toyota City, Aichi, Japan
The Cressida itself, continued as the X90 Mark II in other territories, which was designed up until late 1989 and launched in October 1992. The choice to drop the Cressida internationally and replace it with an all-new nameplate, was because of the Lexus brand not needing RWD competition with a significantly upscaled X90 and spotting an open niche in the US market, of a Buick-style FWD competitor.
MY1993 Toyota Mark II JDM
Development of XX10 began in 1990, with the first mules being built in Japan in late 1991. The first prototypes were built at Toyota Technical Center Ann Arbor MI and first completed on February 5, 1993. Engineering sign-off was achieved in 1994, with series production starting in September 1994 at TMMK.