The FAQ for the VSCODE bitbucket extension says that BitBucket support might come later as a fork of the original extension. https://github.com/Microsoft/vscode-pull-request-github/wiki
But I do see that Atlassian seemed to be working on such a fork but the repository is now archived:
https://github.com/atlassian/vscode-pull-request-bitbucket
Any idea if there is any movement here, or alternatives?