Since it was Shigesato Itoi's Company, Hibonichi, that made the announcement regarding this I suspect that nothing big will happen, and certainly nothing outside Japan will happen.
New Merchandise
A unique event that "has never been done before."
An unspecified "collaboration with another event."
Nothing interesting for the rest of the World, unless you are a true Mother fan.
Lifetime Sales Predictions
Switch: 160 million (was 120 million, then 140 million, then 150 million)
PS5: 130 million (was 124 million)
Xbox Series X/S: 54 million (was 60 million, then 57 million)
"The way to accomplish great things, is to be indefatigable and never rest till the thing is accomplished." - Joseph Smith Jr.