The problem is no gameplay has been shown at all. Until I've seen gameplay I'm not convinced. We have no idea how long they've been working on Bayonetta 3 because they haven't announced a release date and had just shown a really short cinematic trailer and nothing else.
important to keep in mind that lately Nintendo has not been showing gameplay of upcoming games until prettyyyy close to their release. Almost all of their big 2017 games we saw less than a year before they launched. Odyssey at the Switch announcement video, Arms / Splatoon 2 at the January big Switch Event, etc.
It would be very in line with Nintendo's recent trends to show footage of a number of games at the start of the year that will be out in 2018 and haven't been talked about yet. I mean OBVIOUSLY it's going to happen with some big titles we've yet to see as Nintendo currently has very very little announced officially (Bayonetta bundle, Bayonetta 3, Yoshi, Fire Emblem, Kirby being basically it)
In all fairness, the Switch was a new console, so there were bound to be surprise announcements for games releasing in the launch window. Also worth mentioning is the fact that we actually saw Splatoon 2 and Mario Odyssey gameplay at Nintendo's October 2016 reveal initially, which is actually a year gap for Odyssey and 8 months for Splatoon 2 (but it makes sense for Splatoon 2 as the game released with minimal content and that was gradually finished over updates like the Holiday update in December). If we apply the same logic to Platinum who have way less resources than Nintendo, then there's no way the game could release this year, because gameplay wasn't shown last year in December like Odyssey and Splatoon 2 had. At least we knew that these games had made decent progression in terms of content, whilst with Bayonetta 3, this is unknown. I don't think you should be holding out for Bayonetta 3 releasing this year. Nintendo are most likely going to announce new games releasing this year at their event/direct besides Yoshi/Kirby/Fire Emblem.