Board Thread:Spoilers!/@comment-25624943-20141211075940/@comment-24674051-20141217152016

I think the main reason that we might only see Ariel in the present is that, based on the season 3 episode "Ariel", Ariel never had any real interaction with Ursula. Ariel just thought of Ursula as a "mythical goddess" that lived thousands of years prior.

And after he flashback portions of Ariel until present time, it is going to be hard for Ariel to interact much with anyone, since she does not have a voice.

Also, she and Eric are on Hangman's island at the moment, but keep in mind that Mermaids posses the ability to cross realms, so she can appear at any time. And from the Back half of season 3, we know that Emma's power is enough to be able to see across realms (something that even Regina can not do), and now that her power is better controlled, Emma might even be able to send messages across to communicate with Ariel.