I see no reason to do it in CGI. If it were brought back, it would make the most sense to do it in 2D animation, to capture the style of the original Carl Barks comic books on which DuckTales was based. As well as capturing the style of the show itself. Many of DT's episodes were superbly animated -- the work of Tokyo Movie Shinsha, the best animation studio in Japan and one of the best in the world. High-quality 2D animation is gorgeous, and it's a crime that Hollywood is driving it to extinction because of its fixation on the current fad of 3D computer animation. That's like abandoning painting as an art form because of sculpture -- it makes no sense to pick just one instead of letting both thrive. There are some things that are better suited for 2D animation, and I think DuckTales/the Carl Barks ouevre is one. Certainly some cel-shaded computer animation could be used for 3-dimensional backgrounds, sets, vehicles, effects, and so forth, but the character animation should be traditional.
The question is whether Alan Young would be able to reprise the role of Scrooge McDuck. He's apparently done so in video games as recently as last year, but he's 94 years old, so frankly there's no guarantee he'd be, well, available for any such movie unless it comes along really soon. And it's hard to imagine anyone else playing Scrooge; only a couple of other actors ever have, and only once each (Bill Thompson in a 1967 short and Will Ryan in a 1987 short).