Seeing as how a number of people have recently expressed a desire to not go through with the Gamepedia merge and have been alarmed at this site's URL change, I thought it might be a good idea to set the record straight as to what said merge actually means and entails.
After this post has been up for a little while, I'll post a second thread where people will be able to vote/discuss whether they want to go through with the merge. (In spite of the fact that the wiki's URL has already changed, I don't think it's too late for this.) That discussion will not include a poll - instead, respond to the thread saying whether you want the merge or not, including as much or as little reasoning as you want.
What is this about?
In brief, Fandom acquired Curse Media in early 2018/late 2019, which includes Gamepedia. Shortly after, plans were announced to merge the two wiki platforms. Since there is both a Fandom Terraria wiki and a Gamepedia one, this was always going to lead to something being done, though what that is is up to the communities involved.
What will happen if we accept the merge?
(Seeing as how there was a poll 7 months ago on this issue which indicated this as the preferred option, Fandom appears to be going forward with their plans as such.)
This wiki will be archived. This means that editing will be locked, it will be moved to a new URL of terraria-archive.fandom.com, discussions will be closed, and it will gain a banner at the top directing people to the other wiki's location (currently terraria.gamepedia.com, but eventually that will change to have this wiki's current URL - terraria.fandom.com). All of these things won't happen at once - as many of you have already noticed, the site's URL has changed, but editing isn't locked, discussions are still active, and there's no banner directing people to the other site.
What will happen if we do NOT accept the merge?
This is a little trickier. This wiki will stay open, but because the plan seems to be to eventually have all of the wikis under the Fandom umbrella have a Fandom URL (ie. end in ".fandom.com"), we would need to resolve the identical site name/URL conflict.
Additionally, in a departure from Fandom's old philosophy of multiple sites for the same topic, wikis with identical focus are no longer allowed (see also: Fandom's community creation policy). So, this wiki's scope would need to change accordingly.
Other information
Regardless of what happens, the Gamepedia wiki will eventually be moved onto the Unified Community Platform (UCP). This means that in terms of functionality and appearance, the Gamepedia wiki will be similar (though not identical, due to a decade of divergent customization) to this wiki's current form. Notably, this means that discussions are on the table for that site, though since it doesn't look like Fandom forces them to be enabled anymore, it's ultimately up to the administration.