One of the big reasons TSR went bankrupt when it owned D&D was that it made lots of different campaign settings, with adventures in each of them, and it split the player base. Profit per book is way down - costs for design, editing, art, layout, and the stuff is the same, cost per copy is up with smaller print runs, and they sell less books.
So, everything else you say needs to address the financial aspects to have any foundation.
Alienating some existing players, and reselling core books to all the other players, still makes financial sense.
So, higher development costs, additional printing costs for the additional pages, just to sell to the same total number of players. Failure. Plus that means that for some of them they haven't sold the new core books - additional failure.
What is their motivation to all of this?
Sorry, looking at all of this, I can't see anything that makes sense for WotC to follow this as a business plan.