AFAIU they are not ditching C++, they are exploring writing some parts of the engine in Swift using the new C++ interop features in Swift. But a wholesale switch to Swift doesn't seem realistic.

I remember Andreas saying something along those lines in some interview, but seeing their repo[0] doesn't looks like

C++ 64.6%

HTML 22.4%

JavaScript 11.0%

CMake 0.7%

Objective-C++ 0.5%

Swift 0.3%

Other 0.5%

[0] https://github.com/LadybirdBrowser/ladybird

It did seem like an odd decision maybe they thought better of it.