There's no mention of following other collections, although it might just be a matter of time.
Instagram told TechCrunch only that it's "not testing this." However, that only means that the team isn't publicly experimenting with its widened Collections feature at the moment. This doesn't preclude future tests or a full-fledged release.
There are strong incentives to launch this feature, too. Instagram wants shopping to be a core part of its money-making strategy, and public Collections would go a long way toward this. Brands could launch larger virtual stores (versus a handful of products in posts and ads), while social media stars could showcase their sponsors' wares in one convenient place. And then there's the question of thwarting competition. Instagram is already much larger than Pinterest with over 1 billion active monthly users versus 250 million, but this would reduce the temptation to switch to Pinterest when you want to share more than just a photo or two.