I'm a Nissan dealer in Canada, and have been shown the new Frontier on two occasions now. Most recently at our bi-annual product reveal hosted in Chicago this year. I can tell you what ever you want to know about it. 
Coles notes, entirely new truck. Nothing like the European Navara. Picture current Tacoma proportions with a more square face and lights. 
The 4.0L V6 becomes a 3.8 and gets a new 9 speed Automatic transmission. 
Up here in our neck of the woods, we're keen mountain bikers and I do everything I can to support our MTB Community. This is the product we are most excited for this year. Plus also the new Pathfinder because those also fit our needs nicely. 
We have a blackout period when we can no longer order the current Frontier that runs from This February until April 0f 2020. This is usually a sign of re-tooling a plant to get a new model ready. An April start of production would have them on dealer lots for late May, early June.