The whistleblower @Jiorīku said on Twitter that when the iPhone 13 is launched in the second half of 2021, Apple is very likely to stick to the design of the iPhone 12 , including the flat and square frame design, and still include the aluminum and stainless steel middle frame version, depending on the specifics. It depends on the product model.
Like the iPhone 12, the more expensive version will use a stainless steel middle frame. The whistleblower also mentioned that people who want to use both Face ID and Touch ID on the new iPhone may be disappointed, because the current iPhone 13 prototype does not use the technology of under-screen Touch ID .
Of course, this is only a prototype under development. The final retail version has not yet been finalized, and everything is constantly changing. Combined with current rumors, the next-generation iPhone may use a 120Hz high refresh screen, or it may further remove the physical interface on the iPhone.