Language and the ability to communicate using language is essential to humans and their continuing development as a species. As humans continue to evolve, it is only natural for language to continue to evolve and develop with them. Since we still occasionally discover tribes of people living in remote areas of the world, it is not only likely, but inevitable, that more languages will be discovered. And those languages, once discovered and put out into the rest of the world, will influence existing languages and the development of new languages. One could also argue that the use of jargon and other specialized languages such as binary code indicates that humans are constantly inventing new languages.
Communication is the backbone of civilisation,how else will mankind develop if they can't communicate? The developing of new communication has helped civilisation greatly. It has made scientific discovery much easier by allowing communication between universities and their members. It has also improved safety as calling for help takes less than a minute. Mankind will continue to invent new communication as it makes life easier.
One of mankind's strengths is it's ability to communicate and thus share and pass on ideas. This is how we advance. We have the capability of knowing multiple forms of communication and can bridge barriers of communication. So man will always find a way to keep knocking down the barriers that keep us from communicating to each other.
Just because scientists have found a new sign language I don't think that means we will continue to invent other new languages. With the way the wider society is now and how populated the earth is it doesn't make sense to invent new languages. Existing ones will always be subtly changing though I think.