In my opinion would be a good result.
358 days came out when DS was very much wider in terms of demographic and install base.
Very very higher under that point of view.
Plus, it was the first of too many spinoffs (three in a short time, considering Bbs and Re:coded), and this is the fourth spinoff of a brand that SE is stretching too much, in my opinion.
I agree that KH3DS seems a better episode than 358 days, and up to now there is no "better version" coming out (as it was for 358 days with Bbs incoming) and for these reasons I think that KH3ds could compensate those negative points I described, ending with LTD results similar to 358.
Due to the aformentioned reasons, I think that it will debut worst than 358 (less install base) but should have better legs (same LTD)