When will the promised Islamic Caliphate, modeled after the Rashidun Caliphate, be established?

The Caliphate upon the Prophetic Methodology is a prophetic promise that will inevitably come to pass. However, its timing, manner, and place of inception are part of the unseen, about which no clarification has come in the Quran and Sunnah (definition). Muslims must strive and take the necessary means to establish it.