There may not be any specific plan to end the "preaching work" but that doesn't mean that things can't evolve into such an outcome. Indeed, I now wonder if such a thing is probable!
First, if (and it's a very big if) various nations develop case law that includes liability for volunteers, this will put the Watchtower in a bind. They will be forced to deny that publishers are volunteers ( has this already happened in Australia?). If that happens, they may be forced to take action to actually shut down any organized preaching activity from Kingdom Halls or deny that they support it, etc. Otherwise, they could be on the hook for every traffic accident by every Witness that runs over somebody while in field service, every child molested in connection with field service, etc.
Next, they may move all the printing to the internet and claim the "preaching work" is still going on. Having publishers print out their own tracts adds a degree of separation, of protection. They may go on demanding that publishers put in hours ( in general) but put all the onus on local Halls and individuals, away from themselves. Or they may emphasize internet witnessing and escape liability, period. Such a thing could be a real temptation for them.......
Really dumb elders may not realize that they might end up 'on the hook' in such an arrangement .... but word would travel fast after any lawsuits develop.
Folks, this might be the tipping point.