Star Wars Episode 3: Revenge of the Sith - Declare the Emperor
The sceene were Palpatine declares the Old Republic disband and the new Empire is formed. Right after that Obi Wan calls the Palpatine the Emperor. I thought both scene were happening at the same time. So Obi Wan would have no knowledge of the switch of government.
Obi Wan could of easily sensed such a big event through the force. While the dark side my cloud such big events, the whole Republic was viewing the event. Obi Wan would easily be able to feel such a shift in the force.
Also, even if he couldn't of sensed it, he knew it was going to happen. Whether it was right at that moment, or 20 minutes later. It was inevitable, and he knew it.
Obi is a Jedi, Yoda and him were together for the most part and there was a mass communication made by palpatine to destroy all jedi...they probably figured it out/had a feeling. As well as...I don't understand what you're really trying to point out...