The ending of the second movie suggested that it was not the last one. Secondly The 5th Wave book is the first book in a trilogy.
Is the movie part of the trilogy as well? In other words, are there any plans to release the sequential movies?
There are no known plans for a sequel, publicly. Only people that would know are Sony Executives that have not made any public announcement.
The Book Trilogy wasn't even complete by the time the movie came out in January 2016. The 3rd book came out May 2016.
The movie did decently once you figure in international numbers. A 30 million dollar film that took in $95,654,658 in under a month worldwide. Add in additional weeks of screenings, and any profit from merchandise and home release, the film is a financial success. And everything now a days are trilogies (in five parts). Sony has licensed the entire franchise (or optioned the sequels, as standard), so it most likely will happen. But we are not mind readers or fortune tellers, so the answer is a resounding "Not at this time".