It could backfire on them...maybe...
What is the purpose of the Watchtower magazine? To announce Jehovah's Kingdom. Now, if you're printing half of the magazines only for member consumption, how is that "announcing" anything?
I'm hoping to get some family members to think about that when they bring up the subject of how the new arrangement will work.
Most dubs will be all excited about this change (face it...any change is enough to create pandimonium, they live such dull lives) and they will buy all the rhetoric from the stage about what a blessing it is. Think about how they will have to stop and ponder when someone questions why they feel the need to hide half of their "good news" from people. Isn't that the whole purpose of going to door to door? To share the "good news"?
It's been mentioned that this could be the precursor to declaring the preaching work completed...but that is a risky move. To promote the end of the preaching is basically declaring the "end" any moment...and we've seen how those predictions have worked out. To declare the preaching work complete might boost the numbers initially (kinda like 9/11) but in time it will be shown up as yet another missed prediction of how close the end was.
I can see it twenty years from now when a dub is talking about the good ole days of having to go door to door and the young children will marvel at the stories of the field service work...but what will be lost on many of them is that the end still hasn't come...but to some it could be just the nudge needed to push some of them into thinking for themselves when they see the system not ending as expected.