Here is SunGard's, I mean, FIS's take on this:
"It is important to note that to apply these changes, plan documents will need to be amended to remove the language that restricts the use of forfeitures to fund safe harbor contributions. FIS Relius will be preparing good-faith amendments for this purpose in the near future. Since this change is discretionary, an amendment would need to be adopted by the last day of the plan year to which it applies. In addition, an earlier amendment might be needed to avoid violating the anti-cutback rules (IRC §411(d)(6)) depending on how forfeitures are handled under a plan sponsor’s current plan. For example, if the plan provides for the reallocation of forfeitures, then amending the plan to reduce contributions could violate the anti-cutback rules if participants have already satisfied the conditions for sharing in the reallocation of the forfeitures."
Their full explanation:
IRS Relaxes Rules on Use of Forfeitures to Fund Safe Harbor Contributions