Frozen Northern Lights is a new story in the Frozen universe and it's going to have all manner of elements to keep fans engaged while they wait for an official sequel. That includes a book which is being published in July, a new Instagram account and plenty more to be revealed on the site.
Then there's the Lego stuff, kicking off in November 2016 with four animated shorts on the Disney channel. Josh Gad, Kristen Bell, Idina Menzel plus Sven and Kristoff are going to be back. Gad sounds like he's feeling excited in a scripted sort of way.
Lego has been doing great work recently and Frozen is pretty much the best so we're going to go ahead and assume these won't be terrible little cash ins because Disney won't want to damage the brand. It's also safe to assume that more Lego sets are now in the works.