The cover for the new album has been made public. You can see it on this French website
(scroll to the bottom to see a bigger size version). It is a joint work of Uderzo and Conrad: Uderzo drew Obelix, Conrad drew Asterix.
This page also has an illustration from the book showing Asterix and a Pict fighting what appears to be our old friends the Pirates.
There is also a recent group interview (in French, I'm afraid) with the ones responsible for this new book, including Ferri and Conrad, Uderzo and Anne Goscinny. According to Uderzo, it was at Anne's insistence that the series was continued even after he had decided to retire. Several writers were considered, interviewed and asked to contribute a script which Uderzo would choose. Ferri's script was still at an early stage, having only written a few pages, but was chosen since Uderzo liked the idea of sending Asterix to Scotland, something which he and Goscinny had never considered themselves.
Conrad tells of how drawing the story was very "complex, there is a huge amount to draw. It takes up a lot of time. You have to maintain the rhythm". His previous work has struck me as rather sketchy compared to Uderzo's more detailed illustrations, especially his backgrounds, so it could be that he had to put in more of an effort. However, he states that Uderzo "guided me and he came up with the words" to keep Conrad going and finish on schedule. Uderzo himself says that he "only corrected some little things which nobody could have noticed" but they do not mention examples.
They do not describe the plot, all that they will say is that "two women" are involved.