To be fair, the Holodeck was a ST:TNG tecnology not original Star Trek, which puts it several hundred years away by Star Trek's own timeline so it is not an invention whose authors were overly optimistic about.

As for datajacks - some people are investigating technological implants etc., but I think neural-connections that are not anywhere close yet.
The closest is probably in the artifical limb area, but datajacks need a UI that ties directly into the brain and that is a long way off.