Everything is fine. Simon is writing like there's no tomorrow!
Don't know what's wrong with the publishers at the moment. Apart from Penguin in the US have had a 'night of the long knives'! and a lot of staff have been 'let go' cough, cough. So I guess there's no one there now to actually do the work!
There will be a new Ishmael Jones novel, if fact they'll be 2! Simon finished one early last year and has just sent in a third to his agent. But the publisher is a small UK company and they don't do things as fast as the US corp boys do. There also a chance that there might be 3 more Ishmael Jones books... people are talking.
Lets set the Deathstalker 'thing' to rest. There will be no more.
Simon floated an idea, the publisher said 'No, don't want any more'. That's it. (Unless they change their minds.)
Publishers are now run by accountants. The Deathstalker Returns series didn't make them the $$ that they expected, so that's the end of the story. Harsh, I know, I'm sorry, I know lots of people want a new one. But there's nothing that can be done at this end

Simon is working on the final Secret History books and a new project.
There nothing I can say about it apart from the working title 'Tear Down the Stars'. . .