There will definitely be others who try. Mark Zuckerberg may try to come out with a console. Call it the Fast Back. Elon Musk may come out with a console. Call it the M%g7+Q2(H1ÆO±. Or maybe one of us here may come out with a console. I'd call it the Son Of A Bitch. I'd call it that, because I would only want games on it that were so difficult that every gamer would regularly get pissed and yell out SON OF A BITCH! when playing it.
But to get back to the point, many will come. Most will fail, some may succeed. For a time at least. But as for true competition to the Big 3, I highly doubt that will happen. At least not in my lifetime, or that of a lot of the members here.