Seems odd that Curtis would use NODS as a motivation to end the show, especially because not that many main actors were in it compared to what was built on the show at the time. With NODS filming, you would have lost David Selby, Lara Parker, James Storm, Grayson Hall, and Kate Jackson as main players. Outside of that, the other actors in NODS probably could've done double duty like some of the lesser actors from HODS did. Though, to be fair, shooting a show and a movie at the same time would have been extremely tiring for the actors I'm sure.
But, the show still would've had Joan Bennett, Louis Edmonds, Jonathan Frid, Keith Prentice, and probably could've used Thayer David, Jim Storm, Chris Pennock (these last three making up the lesser used actors from NODS).
Curtis was probably tired of doing DS and wanted to move on, but if show running was already left up to Lela Swift, what difference would it have made if the show kept going?