At the end of his second term is a great time to reconsider! But after he's impeached or kicked out at the next election it will be even clearer.
Of course, there won't be any space anyway because the Obama head will be in the way.
(ps I don't think they need any more mountains turned into presidential heads, but if they were to put Mark Twain and Neil Armstrong on a couple of them, I'd agree with the decision.)