Albert Barnes on Luke 3:15

In expectation. Expecting the Messiah. Marg. suspense. That is, they were not certain whether John was not himself the Messiah. They confidently expected his appearing, and there minds were in suspense, or they were in a state of doubt whether he had not already come, and whether John was not the Messiah.

Mused in their hearts of John. Thought of his character, his preaching, and his success, and anxiously inquired whether he did not do the things which were expected of the Messiah.

(4) "in expectation" or "in suspense" (5) "mused" or "reasoned" or "debated"