SPECIFICS:
1. You could upload audio:
a. From audio files (from computer or web).
b. From video files with sound (from computer or web).
c. From YouTube videos with sound.
2. You wouldn't need Imgflip Pro to upload standalone audio, but you need it for GIF + Audio.
a. You could use sound on GIFs free for 5 times, before you need to wait another month.
PROSPECTS
1. It could diversify Imgflip, attracting more kinds of people.
2. It could enhance Imgflip's features, retaining more people.
3: It could bring more revenue for Imgflip.