To be specific, Seaside Farmland is the 22x22 land expansion in the Lighthouse Cove, available immediately after reaching the Oceanside Farm level that was also given a coin release just a short time ago. While the neighbor requirement is still here for the Seaside Farmland expansion, it seems that the requirement itself has been lessened drastically. For instance, I will only have to add two neighbors to unlock the Seaside Expansion for coins. Going back to our example of the Oceanside Farm, this now only requires me to add a single neighbor, when I was formerly asked to add 11 before. Since there's no knowing whether this lowering of the requirements is here to stay or not, you'll want to take this chance and upgrade as much as possible, as quick as your in-game wallet allows.
When you've gathered enough neighbors to satisfy the Seaside Farmland requirement, you'll then be able to purchase the expansion for 1.75 million coins. No one said land expansions are cheap, and if we want to be able to plow more land on that particular farm, it's a price we'll unfortunately have to deal with.
With this expansion's coins release, we're now left with five more expansions that are still only available for Farm Cash. As they too become available for coins, we'll make sure to let you know.
How far have you expanded your Lighthouse Cove farm in FarmVille? How many neighbors will you / did you have to add to your game to unlock the Seaside Farmland expansion for coins? Let us know in the comments.