Maybe the 737-900ER could be but only for domestic flights. It doesn't have the range for transatlantic flights.
I think that is where they are going with that line. I know for damn sure the A321 doesn't have any legs. My airline inherited a bunch of them in the merger, they are not built for high/hot extended flights.
I'm P.O.'d that Boeing shut down the 757 200/300 line and the 717. Both are fantastic planes and they could have probably sold another 50 or so. The 717 market is gonna be taken by the Emb 190/170, which is a hell of a plane, but I think Boeing was in too much of a rush to put all the MD stuff behind them.