To go down a storm means to have great success, which is what they were confident the song would do.
Context: "We start with all the young dudes, a song that julian and I managed to convince the other lads to play, confident that it would be very well received by everyone."
Hypothesis: We start with all the young dudes, a song that julian and I managed to convince the other lads to play, confident that it would go down a storm.
Based on the context, is the hypothesis true, false, or unknown?