This is obviously anybody's guess, but my guess is it will have some effect. I would expect some owners to "trade up" to Grand Floridian. There was a good bit of that when BLT opened.
In addition to the location advantage, I think the fixed week option will appeal to a particular subset of prospective buyers -- particularly those who want to visit during the holidays. It will be more expensive, but for some the added expense will be worth it.
The downside is that the MFs are middle-of-the-pack. When BLT sales opened, one of the selling points was significantly lower MFs. BLT's MFs are still almost a dollar a point lower that GF.
ETA: AKV is one resort where I would expect some movement. If a family wasn't fully satisfied at AKV, they could sell that and buy GF and lower their per point MFs a little. They'd take a hit on the resale, especially if they initially bought direct (and maybe a severe hit if they bought direct recently), but over time slightly lower MFs would offset some of that.