They werent really on the rise at the very moment they split. They had just finished a disaesterous 10th at worlds despite skating well. This is the year many expected them to challenge for a medal, and the Shibutanis who had always been beneath them under 4CCs that year, were the bronze medalists. They had suddenly dropped to Canada #3 after being pushed but controversially held up over Weaver & Poje all season long, including Canadians which they were gifted the win despite an obvious miscue.
This isn't quite accurate. C&P were still a team on the rise when they split. They had just had their best year ever (gold & silver on the GP and a bronze at the GPF, plus winning the Canadian Title!). It's true that they dropped from 7th to 10th at Worlds, which was a disappointment, but it was hardly a disaster since they still stayed in the top 10. Far worse things have happened to other teams. W&P were much more inconsistent in the days when they were competing against C&P, but by March 2011 they had become much better and did move ahead of them.