Games I've seen with interesting mechanics/structure:
Splatoon (EAD Kyoto understands that a good competitive arena battler should focus on movement, not minute details in the guns or slow ADS)
Bloodborne (as always, From's action-RPGs are really complex and of the right difficulty; I bet the action focus for this specific game will work just as well as Dark Souls' defense orientation)
R6: Siege (the concept sounds very fun, though I doubt Ubisoft's up to the task of making it play well)
Codename: S.T.E.A.M. (dull character designs aside, the game sounds like a very nice alternative to Valkyria Chronicles and XCOM, though no permadeath + generous checkpoint system = skepticism)
Cuphead (Konami and Treasure-style boss rush with a surprisingly accurate and original Fleischer-esque animation style...awesome)
Elite: Dangerous (more excited for this than No Man's Sky, as the trading system's still a wondrous exploration promoter, and there's a nice balance of space-sim elements with mapping and room for role-playing)
Overall, I'm most excited for Cuphead, followed by Bloodborne and Splatoon. All three games are fairly unique in this era (boss rush, hardline action-CRPG, first-person cute-'em-up), they seem to provide diverse and involving challenges, and there's a high ceiling of skill that's attainable either through intuition or disciplined play/practice.