Hi Nathan-
There are no "blockout" periods for luxury resorts. I'm not sure how far in advance you can book them, but I would say it is a year, since the points for luxury resorts change every year.
Also using points for luxury resorts like the Grand Floridian or The Poly will cost you more than twice the number of points than if you stayed at a
DVC resort. Also DVC points do not change from year to year where Disney Resorts points keep increasing
In other words, buying DVC to stay at Disney's Deluxe Resorts is not the best idea. If you buy DVC you should want to stay MOST of the time at DVC and occasionally at Deluxe resorts, unless you are purchasing a VERY LARGE number of points. Personally I wouldn't use my points that way unless I owned more than 800 points.