As previously reported, Nintendo are developing a new Flipnote Studio animation app for the Nintendo 3DS, titled Flipnote Studio 3D. You can read up on details of the app here.
Flipnote Studio 3D is scheduled for release this Summer, but prior to that, the old Flipnote Studio community for Nintendo DSi on Hatena will go offline on May 31st. Before that happens Nintendo recommend claiming and transferring your animations to the new upcoming community.
You’ll be able to transfer your Flipnote Studio animations to Flipnote Studio 3D. You can read more about how to perform this transfer here on Nintendo’s Flipnote notice page.