I find now that I've explored all of the currently available biomes I have very little reason to explore anymore
I have a barley and flax farm to I don't need to raid fucking villages. I have carrots and turnips so no need to go get seeds for those from the forest and swamps, I have the boss trophies, I have every weapon available, etc
The only reasons to "explore" now is to get more iron and wood and stone to build up my bases.
I think It would be cool if there would be an update in the future that included more variable and deep dungeons with rewards that mattered, like relics that you could put into a trophy room or maps that lead to buried treasure. Some sort of reason to actually find a new island you haven't been to before and see if it has something you've never encountered.
Each island should have something unique so you have a reason to find them all basically.