Palace say there will be a club announcement at 9am on Friday and developments on Cabaye are expected.
The fee is understood to be a club record £10m, rising to £13m with add-ons, and Cabaye is thought to have undergone a medical in London on Thursday.
Sky Bet suspended betting on the transfer on Wednesday after taking a number of bets at short odds and a completed move to Palace would reunite him with Alan Pardew, his old manager at St James’ Park.
The France midfielder spent two-and-a-half years with Newcastle before leaving for Paris Saint-Germain in January 2014.
Cabaye has struggled for regular football in Paris, starting just 21 Ligue 1 games since his arrival.