Supposedly, that's the end of Shannara. Terry Brooks claims that The Last Druid was the latest he intends to go in the in-world timeline. This series was supposed to radically alter the Four Lands forever, and I was expecting something big. The first couple of books were promising, with the Skaar invasion and the fall of the current Druid Order (the Fifth?); the Skaar were such a compelling, dominant force that it seemed certain that they were going to be in the Four Lands to stay.
In the previous two books in this series, a lot of time was spent bringing players into place and setting up introductions. There is plenty of action, but it all retains a fairly light touch - there is a sense that, although things are happening and changes are occurring, nothing really major has changed yet, and anything that has changed is not necessarily permanent. This is common in series, when you start to look at them holistically; it takes time and words to put all of the characters into the places they need to be for the plot to start really picking up. With The Stiehl Assassin, the plot definitely accelerates.