The assistant will still exist in some capacity, such as Outlook mobile and Teams mobile, but the main app on Windows will no longer be supported as of late 2023, according to Microsoft.

You don't need the Boot Camp Assistant at all to repartition. You can just use Disk Utility (you'll have to make a placeholder FAT/MS-DOS partition, then reformat it to NTFS somehow tho).

Microsoft unveiled its new AI-powered assistant known as Windows Copilot, a chatbot which will work across apps on Windows 11 and is set for a June preview for users.