I'm crossing my fingers for a Switch release, as I said, but online-only would definitely be a strike against that outcome, as it doesn't quite cohere with the Switch's play-anywhere value proposition. And while Ubisoft staying silent on platforms might lead to a timed-exclusivity bomb from Nintendo, it could just as easily (and is perhaps more likely to) set up an imminent timed-exclusivity bomb from Sony.
Nobody is clear on anything yet, but I hope the online component doesn't suggest online-only, but something more like the jump from Xenoblade to Xenoblade X, where the latter was less linear and story-driven but also had an element of online squad connectivity that nobody really used.
I trust Ancel, anyway; he has been consistently the most interesting figure at Ubisoft from its inception and the only reason I keep up with the publisher at all, and even if BG&E2 appeals to quite different sensibilities than the first game did, I think it still stands to be interesting.