Nintendo has gone full "simultaneous worldwide" for releases, and I don't see that ending with MP4 imo. Regardless of how popular Metroid is in Japan (it was simultaneous for Samus Returns, don't see why MP4 would be any different).
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So far, 1st-party for Switch is following the same strategy as 2017, aka: "one "major" release almost every month":
Jan. - Mario + Rabids
Feb. Bayonetta 1 & 2, Dragon Quest Builders (in the west)
March. - Kirby, Hyrule Warriors (ok, it's KT, but still)
April - Mario Tennis, most likely (and Hyrule Warriors in the west, if the release pattern of previous KT collabs are anything to go by).
May - DK Tropical Freeze
After June everything is blank, but going to assume Fire Emblem could be a June title, Yoshi a July or September release, and beyond Summer is most likely something that won't be known until E3 or a Nintendo Direct.
2017 line-up was clearly planned under the assumption that 3rd-party devs would completely miss the boat, as even one game being delayed would have hurt momentum. 2018 is the same so far, from the looks of it, though with a bit more third-party stuff. I'd say that Nintendo keeping Rabbids for January right from the start is a sign they were expecting nothing from third-party during that month.