Rumour has it that AMD will be bringing up to 505 mm² dies to its next-generation "Big Navi" GPUs. Based on the company's RDNA 2 architecture, Navi 21, Navi 22 and Navi 23 all supposedly have larger dies than the RX 5700 XT. The Navi 21 has a larger die than the custom RDNA 2 GPU in the Xbox Series X, too.
https://www.notebookcheck.net/AMD-Big-Navi-GPUs-to-have-up-to-40-larger-dies-than-the-Xbox-Series-X.463200.0.html
QuoteNavi 21, Navi 22 and Navi 23 all supposedly have larger dies than the RX 5700 XT.
Quotethe dies of Navi 21, Navi 22 and Navi 23 will measure 505 mm², 340 mm² and 240 mm² respectively [...] [with a] margin of error of 5 mm².
Navi 10/5700 XT is 251mm². Last I checked, 251 is a higher number than 240 +/- 5.
Also, it's rather odd to compare directly with the XSX die given that that also contains an 8-core CPU and all that comes with that.