Now, I'm almost sure Sir Ridley is going to leave the franchise.
The next ALIEN movie is going to have a SMALL Budget similar to ALIEN V PREDATOR(Paul W.S. Anderson) budget. Like 50-60 Millions.
Sir Ridley Scott STILL get BIG Budgets for his other films. He made his biggest hit(THE MARTIAN) with 108 Millions.
So, He DOESN'T need a new ALIEN movie with a small budget of 50-60 Millions.