Elves in Modern is a very powerful deck in the right hands, and now it can become even faster with the help of Steel Leaf Champion. It can be summoned through Collected Company on turn two already.
There are lots of Elves players, so this card will experience a spike in popularity after the release. But there is also a possibility for revamped Stompy decks -- it's just a perfect card for them.
All these Modern archetypes need something like Steel Leaf Champion, especially against Valakut decks, which can be very hard to deal with. So the solution is in even faster, more aggressive creatures like this one.