There is no current plan to implement such a feature given that they are typically used to convey important information and don't show up frequently. It's something I've thought about though and will consider doing if announcements like this become more frequent.
Actually, I take that back. I was initially concerned people might miss actually important announcements but I just came up with a simple to implement way to handle closing just the current announcement and will do it tomorrow. For reference, the solution will be cookie-based for now so you'll need to close it on each site unfortunately but that will change for logged in users once we decouple the sites from the forum.
Edit: Okay, this should be in now. Let me know if you notice any issues with it!
Actually, I take that back. I was initially concerned people might miss actually important announcements but I just came up with a simple to implement way to handle closing just the current announcement and will do it tomorrow. For reference, the solution will be cookie-based for now so you'll need to close it on each site unfortunately but that will change for logged in users once we decouple the sites from the forum.
Edit: Okay, this should be in now. Let me know if you notice any issues with it!