It seems obvious that the Old type Mystery Schools are extinct to all effects at the beginning of the 21st century. If any are left they have little or no influence whatsoever and, especially, no future. The modern sects that claim to be their followers are numerous, but their influence is limited too. Probably there will still be many of them in the near future as they fill a void that has been left by the conventional religions.
On the other hand most religions -in particular the seven main religions described before- are there to stay. They will still attract many people as they answer an important need. However their influence will be decreasing all the time for many reasons. In particular people are becoming more and more educated and they are not ready to believe anymore in something that is not logical, that they cannot understand because the clergymen tell them that it is like they want them to believe.
But there is still a large percentage of the population who is willing to follow their churches. This is the case of the less educated people who will go on believing what they are told to believe, as they have always done. There are also some others who, although they do not believe all that they are told, go on being active members of their churches because it is easier than trying to understand more.
However what is now an increasing minority wants something more. These people are ready to try to know more about religion that in the past, they want to understand what they are told and they are not ready to accept as true what they do not understand.
These people do not necessarily want a new religion but they want a new approach and they will find it, sooner or later.