Although I don't believe the salesperson referred to in the OP was accurate, particularly with respect to assigning units at a home resort, the salesperson was almost certainly accurate that big changes are forthcoming.
It is pretty clear that Marriott will be making some changes in June or, if the new program is delayed, sometime soon thereafter. What will the new program be? We don't know very much. What does seem pretty clear is that there will be a points program that will apply to many (most?) future timeshare sales by Marriott, will involve exchanging based on points and will be available to current Marriott timeshare owners - for a price. That price is supposed to be nominal (whatever that means) for those who have purchased their timeshares from Marriott and probably quite a bit more expensive for those who have purchased resale. The changes are not likely to affect the privileges that we are all guaranteed by the legal documents of our respective resorts. Rather they will likely offer an exchanging “enhancement” for those who wish to participate.
How do we know that some big changes are coming? We first heard about the changes almost two years ago. I have had some clearly-in-the-know Marriott people confirm those changes to me on several occasions over the past two years and I reported that information here each time. What we are now hearing is about the same as what I originally heard way back when. The only difference is that the effective date has been delayed by about six months, not unreasonable for such a big project in a down economy. Further, Fletch, a much respected member of the TUG community in past years who has just resigned from a very lucrative sales position at Marriott, has confirmed that a new program will be forthcoming this year (see the above link to his posts).
All we can do is wait to see what the details are and continue to speculate.
As to whether the changes will be good or bad, I'm certain the answer is a resounding YES! There is no way to be sure, but I'm guessing that platinum week owners at top resorts who bought from Marriott will love the new program and resale owners of bronze and silver weeks will hate it.