Will this be added in the future, or maybe not at all?
EDIT;
This probably applies to other ports as well, but this was the official response given when I added a request to the tracker.
Which engines are built in releases are decided by the release manager, and
is the same for all ports. So as soon as the Mohawk is deemed ready
enough, it will be enabled for all ports, including Dreamcast.
If you compile the port yourself, you should be able to enable Mohawk
engine with the configure option --enable-mohawk (or --enable-all-engines).