Lexus isn't quite coming out and saying it but the ES appears to be heavily influenced by the GS based on this statement from the announcement, "The sixth-generation ES model introduces a progressive new design featuring the Lexus signature spindle grille and a new dynamic driving experience."
The spindle grille was first introduced on the GS plus the concept of an everyday Lexus actually having a driving experience was floated in earnest at the Los Angeles Auto Show launch (and reinforced later in Las Vegas at a media launch event).
Looking at photos of the grilles side-by-side you can see some minor differences. The headlight compartment on the ES has a slightly different take to it. The GS grille has a more pronounced bend along the side, too.
We'll have to wait until the live unveil on Wednesday (or the inevitable leaked photos over the weekend) to get a true sense of the similarities and differences between the two stablemates.
The Lexus press conference will take place on Wednesday, April 4th at 11:20 a.m. EDT at the New York International Auto Show. (It will be on display in the Lexus exhibit from April 6-15, 2012.) No plans have been announced for a web chat or anything similar.
That the Lexus is being introduced first ahead of a hot new Toyota sedan could be seen as significant. It appears the Lexus ES is not going to be the game changer that the unnamed Toyota sedan (could it be the next-generation Avalon as some suggest?) is going to be because it gets introduced first, which means it could get lost in a whirlwind if the new Toyota is as significant as some think it might be.