Looks like Arnold thinks like many of us fans out there and won't be doing EX4 without Sly.
He told EW that he will not appear in The Expendables 4 without Sylvester Stallone, who has reportedly departed from the action sequel. “There is no Expendables without Sly,” says the Terminator star. “I would never do the movie without him, no.”
Arnold is out so is probably Statham who received kudos from Sly on his Instagram account for being a standup guy and having Sly's back, so we can safely assume that he'd be out too if Sly was.
Here we have it, EX4 seems to be going back to either being a dead project again or becoming a DTV franchise...RIP.