I think the first novel is a little too dense to be done justice in a single 10-15 episode season of television (which appears to be standard, these days.) Possibly the thing to do would be to split it up into it's three constituent "books"; 'Dune', 'Muad'Dib', and 'The Prophet'. That give you three seasons, each with an established beginning and end point, with plenty of material in the glossaries to elaborate where needed. More than anything it'd mean Fenring could at last get a significant role as for such an interesting character, he was sadly neglected in both the mini-series and movie.
If the show is still going by the time Paul takes the throne then you can probably squeeze 'Messiah' into a fourth season and 'Children' into a fifth and sixth. I doubt they'd go further than that, but I as I said before, *if* they were to attempt it, the smart move would be to mostly skip over 'God Emperor' and get right into the Honored Matres for two more seasons. No clue how to end that though. Honestly I'd rather they leave it with the same ambiguity with which 'Chapterhouse' concluded.