All I heard is that there were Antutu benchmark results, one for the Samsung SoC and one for the Helio X20.
The Samsung SoC turned out to be the Pro 5, and the Helio X20 is yet unknown.
Maybe it’s a MX6 or a ME5, who knows. Probably Meizu will give a statement by the end of the year, when the first Helio X20 phones will be announced. But I am just guessing, though it would make sense if the replace the MX5 before it’s one year old, right now Meizu is found of doing so.