I think this will reduce preaching a lot.
For the really zealous, this change doesn't really matter. They were trying to bait people into the recruitment process Bible study anyway.
For the less enthusiastic and zealous, this will reduce service hours. There are a lot of dubs who love the invitation campaigns because that's a lot better than offering mags or actually talking to people. These dubs will not be happy about having to start Bible studies. They'll be hiding under a rock instead.
So these dubs will continue to simply offer mags. But with much less issues and no monthly offers, that'll get boring pretty fast. So less hours in service as they can't arse themselves to go out.
On top of that, those with huge magazine 'routes' will get a lot less easy hours driving around territory placing mags with people they already know will take them. These hours will be lost now, or they'll have to do more cold calling door to door....
Wonderful news!