I haven't gotten that far yet. The first task for the new year, just because it's a new month and thus a new season, is to make sure that I've got Deerling in my party in each of my games so they'll change forms and I can show them to the scientists.
Beyond that - in my White, I'm in White Forest hunting for a couple of Ralts - one male and one female, either to build into a Gallade and a Gardevoir or to breed for others to build into a Gallade and a Gardevoir. I spun circles for about an hour this morning, but didn't find one, so if I don't find one before the day's out, they'll be the first for the new year. In Black, I'm at the entrance to Chargestone Cave, but I'm not sure when I'll get back to that. It probably won't be for at least a day or two though, so whatever I catch first in there will be the first for the new year. Probably a Joltik, though hopefully a Tynamo.