According to Movietele (Italy) (translated via Google):

In Morocco, Tuesday, October 29, filming of  Waiting for the Barbarians  by Colombian director and screenwriter Ciro Guerra (which in 2015 directed Elbrazo de la Serpiente , Oscar nominee for Best Foreign Film), begins.

…

The cast consists of Mark Rylance, Johnny Depp, Robert Pattinson and Gana Bayarsaikhan. 

…

Andrea Iervolino said: 

“I am very happy to produce this film, with such an extraordinary director and cast Ciro (editor’s note: Guerra) is a visionary and very intense director in every shot and it will be really interesting to watch him direct actors like Mark, Robert and Johnny: I’ve had the opportunity to meet Johnny before and he has the ability to contextualize everything he does in a unique way and he is lightened by the conventional film industry formulas that dictate the rules of projects that are traditionally made “ .

Monika Bacardi commented: 

“Producing this film makes me very proud: being able to put together a cast of these proportions is an important milestone for our film journey, and then directed by an extraordinary director like Ciro, whose job is absolutely inspiring for all of us The expectations for this project are very high and I can not wait to see the results “.

Depp added: 
“In this era of democratic entertainment, I admire Andrea’s ethical imagination and I look forward to collaborating with him independently, farsighted and that will adapt to the principles of our respective entities”.

So it looks certain that Joe Alwyn is no longer in the cast.  I did notice his name was removed from IMDbPro this week.  And Monika Bacardi isn’t wrong – the expectations are quite high – well at least mine are.  

Thanks to @itfansofdepp for the heads up