This is a tough question to answer. I think it depends on the type of Protestant and the individual. We all know there will be many people who think they will make it to heaven only to find out they will not. I believe a very large portion of those will be Protestant. Believing a false teaching or heresy is just as bad as being an atheist, if it keeps you from heaven. I think there are also many Protestants who have found their spiritual path, so to speak, regardless of the incompleteness or incorrect teachings of Protestantism as a whole. In other words, will there be Protestants in heaven, yes. Will there be Orthodox who are not in heaven, yes. I think it better to never hear the message of Jesus than to hear the wrong message, because then it leads people in the wrong direction. A false belief and hope; however, I know many people I am confident will be in the presence of God when they pass from this world, who are Protestant.
So, to answer your question as best as I can…it depends.