I wouldn't "do" anything, since it's beyond my control. It is, however, a ridiculous idea. With Ben Hardy filming the new X-Men film and potentially moving onto bigger things, I wouldn't be opposed to Thomas Law picking up the baton again. It's worth remembering that the role of Peter Beale has been recast several times now (although the first few were played by children). Plus Thomas had a longer run than Ben.
As has been mentioned above, it would look so awkward if he came in as Johnny Carter and shared scenes with Ian Beale. Look at how some people picked up on the weirdness of Fatboy interacting with Claudette, having shared scenes with the actress when she was Grace Olubunmi.
Why would he return as Johnny anyway, when Peter is a vacant role? One that he has acted in before AND possibly returning with Lauren.
If they want to bring Johnny back it seems probable that they'll go with a recast.