Yes, "the future becomes the past". But I think the point of this article to to reconcile this concept with experiments that affect the past.
From page 17, discussing such experiments:
"Many of them in fact assume that the future already exists (if the future did not already exist, it would of course not be able to influence the present or past). Our claim, by contrast, is that the future does not yet exist; at present the future is merely a set of possibilities."
Still, it sounds like philosophical wishy washy. What does "exists" even mean? If a "set of possibilities" exists, you could equally say "the future exists".
From page 17, discussing such experiments:
"Many of them in fact assume that the future already exists (if the future did not already exist, it would of course not be able to influence the present or past). Our claim, by contrast, is that the future does not yet exist; at present the future is merely a set of possibilities."