The release announcement for Mercurial 2.0 mentions a new graft command, which on first sight looks similar to the transplant extension. Wh
Graft uses Mercurial internal merging, while transplant relies on patch mechanism. Therefore graft should be able to handle three-way-merges better than transplant currently does.
From the documentation of hg graft it looks like opposite to the transplant extension graft only handles branches within the same repository but can't handle different repositories.