Nothing like that. He's just a very good Championship keeper who could be PL level keeper if he keeps developing and is coached well. That in itself is much better than what we have had recently.
For the probable fee involved in getting him, he would be an excellent acquisition. If we have shit loads of money, id say go for the Villa keeper or bring Hendo back. But such is life, we don't and are back in the Championship.
Johansson for me, is about the best pound for pound keeper that we could get for the money we have available especially when we need money to be spent across the full team. That doesn't make him the next Yashin though.