Terry Gilliam's next film now looks set to be The Owl In Daylight (not to be confused with Owl Stretching Time), blending a biopic of Phillip K. Dick with an adaptation of his last, unfinished work. And unlike competing Dick film Panasonic, this one seems ready to throw plenty of Valis into the mix.
The script is being written by Tony Grisoni and Gilliam, and Electric Shepherd Productions are expected to produce. Currently, it looks like Paul Giamatti will play PKD - this bit is old news and is cropping online in all manner of places.
[EDIT: There is now a crucial update to this story]
As for all of the other 'next Terry Gilliam films', it seems that funding for both Good Omens and Anything For Billy is provisional, and that circumstances, sadly cannot provide the necessary; The Man Who Killed Don Quixote is at arm's length, though likely to go into production for Jeremy Thomas later in 2007; The Defective Detective is getting a rewrite, to distance it from Tideland, by Fisher King writer Richard LaGravenese.
More on all of this very soon... in the meantime, there's much, much more about Gilliam on film ick already, a lot of it rather exciting.
[EDIT: Yes, yes, I know there's only one L in the post title and there should be two. It's not without good reason however - there was a link on another site with a single L in the URL and all their readers were missing out. I swipped over before other people linked, and now there's plenty links, all one L - so what can I do?]