While the change in the law means that the reduction in time is all but a certainty, it does not occur automatically. Your boyfriend needs to have his sentenced modified. A modification can occur in one of two ways, either by a hearing or by stipulation.
For a hearing, the attorney would need to draft and file a motion. After getting the motion filed, he would then need to contact the judge's assistant and coordinate a hearing. Then, of course, he would need to conduct the hearing. As you can imagine, this takes a fair amount of time and effort.
For a stipulation, the attorney would need to contact the assigned Assistant United States Attorney (AUSA). The AUSA would then draft a stipulated agreement for the sentence reduction. After the stipulation is drafted, it would be forwarded to the judge for his signature. This is a quicker and easier method but it does still take a bit of time and effort. From what you have described, it sounds like the attorney is pursuing this method.
And yes, assuming your boyfriend meets the criteria of the change in the law, it is very likely that he will get the sentence reduction.
Please let me know if anything requires clarification.
Also, several customers have asked how they may direct a question to me in particular. If you specifically want me to assist you in your legal matter, just put "FOR JOSEPH" in the subject line and I will gladly pick up the question as soon as I am on-line.