Since there had actually been a telescreen in that room all along, the thought police probably heard Winston and Julia mention something about O'Brien, so I think he is going to end up being put into prison too. I think that the three of them will be put into a forced labor camp and they will try to organize a rebellion with the other prisoners because they are going to be surrounded by people who are also against the party as well. I do not think that they are going to be succesful in their rebellion though in the end.