Don't know if it means anything but was just reading this link:
Mercedes-Benz Enters Global Pickup Market With X-Class - PickupTrucks.com News
And it mentions how the 2018 Frontier will have a new ladder frame in the last paragraph:
"There's no doubt it will be quite a while before a Mercedes-Benz pickup truck is sold in the U.S., but we will be seeing the new ladder-frame Nissan Frontier next year. "
Also if I recall correctly, a couple of months before the Tacoma was redesigned in 2016, it didn't sound like some of the Tacoma forums were expecting any changes. So think Toyota might have announced it kind of late and there were no rumors or anything beforehand as well.
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Forgot to mention, kind of funny but when someone was talking about cars and pointed to my Frontier they mentioned how I had a preference for new cars/trucks. (they were talking about how they only buy salvaged/retitled vehicles)
Didn't bother telling them that my Frontier is almost ten years old but took it as a compliment that they thought it was a new truck. One of the perks of not having a redesign in a while and think that in general trucks age well.