Let's see. Back in December:
Will players be able to have romances and marry each other in the game?
The Elder Scrolls Online does have a mechanic to strengthen bonds between adventurers, but this is not necessarily romance or marriage. Two players can perform a ceremony and receive rings from it. If they wear those rings while adventuring together later, they will also gain bonus experience.
I don't see anything about being able to get the rings only if you buy the Imperial Edition, that wasn't even announced at the time. There is nothing saying that you can't get the rings in the game. Maybe sooner with the ce, but not exclusive to it. Chances are people aren't going to rush into using it. It sounds kind of final. Hopefully there will be more information out. Sounds like you can have more than one pledge, but only one "counts" at at time.
Does the friend I decide to perform the Rings of Mara ceremony with also need to have purchased the Imperial Edition?
Only one copy of the Imperial Edition is required. When players purchase the Imperial Edition, they receive the Pledge of Mara, which is the item they use to get the Rings of Mara. Only one Pledge of Mara is required—both people do not need to have it.
The pledge can be equipped for use. Two characters can approach a Shrine of Mara within the game. While standing on sacred ground, the character with the pledge can target the character without and then use the pledge to evoke the Ritual of Mara. Both characters must agree to share this commitment. Upon acceptance, a celebration occurs and the rings are placed in each character’s inventory. The rings are marked with the name of the matching character. While wearing the ring and adventuring with the corresponding partner, both characters will receive a bonus to their experience. This bonus stacks with other, similar effects; however, players cannot stack more than one Ring of Mara.
Each pledge can only be used once. The names on the rings cannot be changed. This union is forever.