For what it's worth, regardless of the outcome of the suit, there is still a reporting requirement when multiple handguns are purchased from the same dealer in a short timeframe. That requirement has been in place for many years and applies across the board--not just in the 4 states mention. I don't believe it would be affected by the outcome of the suit.
The ATF was trying to force gun dealers to do this on long guns, AR's, etc. and it went to Fedl Court, and recently the Court it was ruled that it was illegal for the ATF or anyone else to do this.
There is no mutiple gun reporting requirement, unless a specific State is trying to do it.