Well at the very least we know Ninty has to fill their 2015 portable lineup with quite a bit more, because given what's announced so far it's pretty darn barren.
I do think at least one of those could be DKR2. GS sadly isn't likely to fill that void as GS4 would probably be released in 2016. I mean, unless they do a Dark Dawn 3D or something.
I'm kinda expecting a couple of other announcements as well, I'm just not sure what else they could have hiding. Metroid is not something I think would come so soon, because if one is in development it was likely only started post-E3 2014, since they apparently had nothing going on Metroid-related at the time. There is both Xenoblade games of course. For new things, maybe an FE remaster? (Path of Radiance / Radiant Dawn, perhaps.) Another possible option is DK64 3D for a remaster (that's one of the last major N64 games that could still get a modern remake).
There's other things we can probably eliminate. Anything new from IS; no Advance Wars or new Fire Emblem (except maybe a Fire Emblem remaster). They have too much on their plate right now finishing Project STEAM, and FE X SMT which we must assume is still in development unless otherwise stated. And even then, like with Metroid, they specifically said that they have ideas but aren't working on anything right now. F-Zero is likely not happening anytime soon, and Metroid might, but I don't think we'd get an announcement yet.
Oh, there is Animal Crossing Wii U. That's another very likely announcement for a game coming out late this year. A new Rhythm Heaven could also be possible.
Based on how much they'd have to announce for this year alone, unless Camelot got major help, they might not be able to announce a GS4 yet. Unless they plan to re-release an updated Dark Dawn for 3DS this year, in which case they'd probably tease GS4. (And no, GS4 wouldn't be the same as Metroid and Advance Wars being mentioned and brushed off as "Oh, we plan to continue these but don't have anything in development now"; no one has commented on GS at all.)