Mistwell
Crusty Old Meatwad
It isn't any evidence at all. Net revenue isn't profit
While that is true that it isn't profit, it's much closer to profit than you're implying. It's the money left from sales after you deduct the sales expenses and cost of the goods. That's what a lot of people mean when they say profit.
At some point, the following becomes true:
Almost everyone who plans to own the core 3 books owns them.
Not really. While the market is not infinite, it appears to have so much room to expand that it can expand for an incredibly long time such that it might naturally be time for a new edition prior to the expansion of the market ending. A lot of WOTC's sales appear to be from new buys to D&D, younger players who have never played D&D before.
Game stores don't want to pay up for the core 3 books because they'll get undercut by Amazon/BN and they'll mostly just take up shelf space.
This assumes people are not coming to the game store to buy a board game, seeing the new D&D game there that they've read an article about, and deciding to buy it. It also assumes the Adventurers League isn't working to generate new sales with customers coming to the game store to play - which all accounts say is untrue. ICv2, which measures game store sales (and who coincidentally is behind this interview), indicates sales remain strong in the retail stores. So, at least so far, your analysis is not holding true from what I can see.