The invite is to an event on October 11th, with the event to be live streamed as usual on the Samsung YouTube account and their samsung.com/galaxy site as well.
"Capture the fun with Samsung as the company celebrates the launch of the new device".
It is easy to interpret the wording of the invite as a sign Samsung will release a device with four cameras. When someone asked "both front and back", @UniversalIce responded with "all back".
We also know the company is set to put more focus on its mid-range devices, so it may be this event is specifically for those upcoming phones. The first response to that tweet is someone sharing Samsung's "4x fun" invitation.
Samsung did just give its latest smartwatch the Galaxy moniker, so it may be a separate part of the business that's also being absorbed into the G name.
Samsung normally makes Galaxy A series announcements in December, so while slightly earlier than normal, an October unveiling wouldn't be completely off schedule. Exactly what each of them will do remains to be seen.
The "4x" matches the number of cameras.