I think it will hasten the government to negotiate in good faith because apparently, it has the backing of Uganda. As of the end of January, 7,000 Ugandans entered near Juba at a place called Nesitu. There are about 16,000 Ugandan troops now in South Sudan.
With that muscle power, Kiir has no incentive to talk peace. If these troops were not there, I think some compromise would be reached because currently the rebels and the former detainees are the ones coming with an agenda for reform and what should be done.
But the government goes through all of this without a piece of paper saying what they are offering because they say they agreed to meet the group and they should come with what they want to see changed. The government stands for the status quo.