As for the story, not much was revealed except there will be a time jump with the description saying “Jumping forward several years from the events of season 2, season 3 takes place at the height of the War of the Elves and Sauron, as the Dark Lord seeks to craft the One Ring that will give him the edge he needs to win the war and conquer all Middle-earth at last.”
The five year plan is said to be in place but that description makes you wonder if they condensed that plan to just one or two more seasons as all indications are the ratings for the show are lower than Amazon was seeking. Technically the entire show is nothing but time compression considering its covering the Second Age with events spanning thousands of years so a time jump isn't as dramatic as it would be for most shows especially since I am sure they still plan on using the same human characters and their limited lifespans so maybe looking at ten or so years at most. The end game for the series remains the end of the Second Age, as shown at the very beginning of The Lord of the Rings trilogy with the defeat of Sauron.