Bittrex may not change it now, and that would be okay if that's how it has to be, but they'd eventually change it when Aeon gets more popular probably (and in the worst case they'd be the odd man out). The key point is that if it isn't changed soon, it will be nearly impossible to change in the future when Aeon is on as many exchanges as Monero, for example.

I don't think it would confuse anyone actually, since you already type "Aeon" into the search bar regardless since its the name of the coin as well as the ticker. The new ticker would be alongside the same name and people would easily figure it out on places like CoinMarketCap, for example. Most people would probably notice just from Bitcointalk/Reddit/Slack/IRC/etc.

I don't think being afraid of a single exchange refusing to change the ticker is something to put so much weight on, since years from now they might not even exist for all we know. The most important thing is to consider whether the ticker is preferable, and I personally think it would be a large improvement as a four letter ticker isn't very pretty.