Hopefully, the Senators' petition will do some good.
As a practical matter, I think there are enough votes in the Senate to get legislation increasing the limit to 500 passed, but it's a "no-go" as far as the House of Representatives is concerned. The ugly truth is that it won't pass because, by increasing the patient limitation, the cost of medicare/medicaid will increase. Of course, if the mandated treatment was probuphine then overall costs would probably decrease, but nobody gets elected to Congress by favoring just one company (even if it makes sense).
The Department of HHS is already in the process of adopting revised regulations that don't require Congressional approval (doubling the cap, etc.). The final regulations adopted could include a higher number (e.g., 500) for the patient cap, but I just don't think it will. Politics.