Will there even be a BF ad or will it just be weekly discounts that we will need to follow?
We don't really know. Each store will do their own thing. Some will just have a normal weekly sale that week. Others might try some kind of shorter 3-5 day BF sale where they can call it a true BF sale but it spreads things out over multiple days. Some might have an online-only 1- or 2-day sale.
The issue will be if any of these longer sales have really hot doorbusters, they're still going to draw big crowds when the store opens on the first day of the sale as people don't want the deals to sell out before they get there, so if stores are serious about trying to avoid massive crowds, they really can't offer the kind of deals (at least not in stores, online is fine) that traditionally draw those types of crowds.
So basically say you're Target, you can't say you're concerned about having big crowds but then have a $99 50" 4K TV in your week-long BF sale and not expect people to line up the night before the first day of the sale. The whole thing is going to be very interesting.