It's happening as we watch. Last night for example, Bo looked like the offensive leader out there, especially in the first half of the game where the Sedins had been less noticeable. He will take over by attrition, by getting more and more icetime, especially at crucial parts of the game. When he came out on the ice it was like the first line was on, as he was driving the play. He is at or very near to their status now, and will match or supercede them by the end of this season, perhaps even sooner.