Shikaku and Shikamaru are without a doubt the most intelligent people.
Twice Shikamaru has defeated people superior to him through sheer intelligence (Temari, Hidan). He could decipher under extreme pressure how Hidan operated. He saw through Obito's Gedou Mazo decoy. He will likely develope a plan against Obito.
With only a short time of learning the abilities ofother villages and with only a day of fighting together, Shikaku could devise a strategy to stop the Juubi in its tracks (while yes it evolved, he had defeated its weaker form). Additionally, he had planned the Chakra sharing that Naruto did... A back up plan.
That being said, Madara may be one of the most manipulative individuals, but he is not the smartest. With the information he had gathered as well as the unplanned events (Obito appearing) he would have had to wait longer. Even after that Obito had basically double crossed him had it not been for Kabuto.