I would say "no" here. Neither one of us have tried that (we stick to stable file systems and btrfs has a history... I'm joking of course (but it has a history...)
That being said, the installer will try to reformat your partition to ext4 if (it's not already) the moment you choose it to be the root partition. As btrfs is supported by the kernel, you could probably convert the file system in some way directly after installation (before rebooting) and it should work, but that's just theoretical. No one has checked that yet. Want to be first?