Let's suppose I own 100 points at OKW and 100 points at VB.
Assuming I'm new, and haven't banked anything forward, at 11 months I have access to 200 points at both resorts for a stay at that resort.
So, I make a ressie at OKW which uses 200 points. Then, at the 7 month window, I could call MS and switch any or all or my available 200 points at VB to the OKW reservation, thus freeing up the OKW points.
The only problem is, I don't see any advantage with doing that. Now I'm stuck with 200 OKW points, all of which need to be used before the end of the use year, because I cannot unborrow the 100 OKW points; the only think I might still be able to do is bank 100 of the OKW points forward (and that would depend on the banking window).
If you really, really, really want to purchase at the future BCV resort, then you should probably just wait for that resort to start sales. On the other hand, if you've really got the DVC bug, and if you are willing to take a little risk of losing a little money, then purchase a resale now and when BCV opens up, purchase there and sell the resale. The risk of losing money comes from the commission you might have to pay a real estate agent to sell the OKW points - that would largely depend on whether points continue to hold value against new sales, whether you use an agent or do a "for sale by owner" or even whether you consider that the possible loss in the transaction is small or non-existant when compared with the money you saved by using points for accomodations rather than cash over the next few years (that's a mouthful).