There are significant legal barriers to having a resort leave BVTC under the current contract terms and then rejoin BVTC2 (basically, RIV's terms in the trading association). The barriers and impacts are such that it is safe to assume it will not happen, because the reward for doing so will bee a lot less than the costs of making it happen, even looking at a 2042 timeline to make it make financial sense.
Very unlikely, true. But not guaranteed.
It's pretty safe to assume that direct buyers will have use of current and future resorts, as that becomes a big selling point.
If, for example... it's 2028, they are selling Reflections. And they decide to cut it out of participation with the existing DVC club, truly starting DVC2, so past buyers can't trade into Reflections -- That would mean the Reflections buyers wouldn't be able to trade into all those existing DVCs, and it would also mean that a Reflections buyer would have uncertainty about their own ability to use future resorts.
Thus, the ability to trade among all past and future resorts is a major part of the sales pitch of DVC. It will likely remain for direct buyers.
But, not necessarily with DVC club trading, Disney has more and more reason to restrict resales more and more. Basically, you have an ever growing inventory of DVC points to sell, as Disney builds more resorts. While the potential market of buyers isn't necessarily growing as fast as they are producing more units. (ie, the most passionate buyers already own. It's not something you re-purchase ever couple of years like a phone.). So you're effectively producing more supply while demand may actually be shrinking. Oversupply will cause resale prices to plummet. (You eventually get people nearly willing to give away their points to avoid the annual dues).
Disney has a monopoly on the ability to sell direct points, while resale is true free market. So if the free market prices resale at $60 per point (for example), how do you convince any buyer to pay $200 direct? You need to find more and more ways to make resale less appealing than direct.
The Riviera restrictions are a major step in this strategy. As each new resort includes the Riviera restrictions, and as the older resorts get closer to expiration, the appeal of direct grows compared to resale.
So where does that bring us? By the time we hit 2042, the resale restrictions will be a major impairment on resale purchases. Those restrictions alone may be enough to push direct buying. As we get closer to that time frame, I wouldn't be surprised to see Disney gradually remove "blue card perks".
But in the near term, Disney will continue to primarily use blue card perks, Moonlight Magic, AP discounts, to incentivize direct purchases. And if they can find other ways to discourage resale within the bounds of the contracts, they will do so.