In theory, as long as you maintain ownership at your current level.
Even as they have adjusted points levels, they have allowed you to keep level you were at in program (owner,select,executive....)

But doesn't prevent Marriott from devaluing.
For instance, I get "lifetime" Platinum based on the point value I own (I have enrolled weeks so I didn't pay anywhere near what points cost now)
But as we all know Platinum is really the old Gold.

And the conversion rate will stay the same.
When I bought, I could convert my week to 110,000 points which used to be a lot of points. Would use to cap off a travel package or the magical anywhere in the world package back in the day.
Now that is hardly anything and I doubt anyone coverts.

So 1:40 may seem good now, but a few years might not be that big

And terms also say Marriott Vacation Club could end relationship. Remember they MVCI(VAC) and Marriott(MAR) are separate companies. Don't see it happening but nothing prevents them from ending relationship.