As far as I know they were planning to make Sourcery with DAvid Jason again as Rincewind but because of scheduling conflicts Jason was unavailable to play him so instead they made Going Postal. So it could be that if Jason is available now they will make Sourcery
Did you notice that the dragon scene was ALWAYS the same, running a bit like this: Shot of Merlin coming in
Shot of dragon
Dragon saying somthing about destiny
Merlin saying somthing to the contrary
Dragon being angry
Merlin being angry
End of scene
Well they don't match up to my imagination of the books and I don't think anything will ever do that no matter who makes them and how much is spent.
But - there's a lot of effort been made to get the right feel and to try to stick to the storyline as much as possible and to that degree they've done well.
I'm a big Bernard Cornwell fan and frankly, some of the liberties that were taken in making the Sharpe TV series are just awful. Bernard sold the rights and had very little control over the making. Terry at least is working with the production company.