If I had to bet my paycheck, I'd say The Irishman will be better on paper than it is in execution.
Scorsese is still capable of making very good films, but he's well past his prime. Shutter Island, for instance, is a decent enough flick that flirts with greatness, but disintegrates into cliched flashbacks and conventional twists in its final act. Ten or 15 years ago, Scorsese would have been more sure-footed and original.
He never makes bad movies, but he hasn't made a truly great narrative film since Bringing Out the Dead, and that was over a decade ago.