I don't think that there will be any other Tolkien films made by PJ, or any other professional film company. The Rights to the Silmarillion and presumably Tolkien's other writings belong to his family, who's priority is maintaining Tolkien's legacy over making money.
I also don't think the Silmarillion has the fan-following to put pressure on Film companies in the same way that they did for the Hobbit, The Hobbit is a children's book that most people are familiar with in some way. The Silmarillion, and Children of Hurin to a lesser extent in contrast seem to be books for the Tolkien fans, I've personally never come across anyone who hasn't read LotR that has read the Silm.
Plus I think it would be refreshing for Tolkien's other works not to be made into a film- as literally every
piece of popular literature is adapted for film or tv now