They've just confirmed that Brave will become the new default browser going forward, but existing installations aren't modified in any way in that regard.
A piece of advice for anyone that sees this warning message during an update after installing Brave following their official instructions:
N: Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'https://brave-browser-apt-release.s3.brave.com stable InRelease' doesn't support architecture 'i386'
Head over to the installation page (linked in the post right above mine) and run the third command that you see for Ubuntu installations, with one minor modification:
- echo "deb [signed-by=/usr/share/keyrings/brave-browser-archive-keyring.gpg] https://brave-browser-apt-release.s3.brave.com/ stable main"|sudo tee /etc/apt/sources.list.d/brave-browser-release.list
+ echo "deb [arch=amd64 signed-by=/usr/share/keyrings/brave-browser-archive-keyring.gpg] https://brave-browser-apt-release.s3.brave.com/ stable main"|sudo tee /etc/apt/sources.list.d/brave-browser-release.list
^^^^^^^^^^