I dont think it will be Paul Bearer, If he was still on ECW he would be a face and the writers of the shows apparentley had no idea who was going where. So if you take that into account creative would have had to pitch the idea of bringing back Bearer then try to get him back. I doubt that could have been done so quick.
I do think they may go with another brother storyline which could be possible, They could have had that planned for months and were just waiting to vring the brother in at the best time.
That guy would be perfect for it.