This creature could see some play considering the amount of playable Dragons that exist in the metagame alongside it, including the ever-popular Stormbreath Dragon and many different options for Dragons of Tarkir. Alongside a card like Dragonlord's Servant, which makes Dragon spells cost 1 colorless mana less to cast, Scaleguard Sentinels gives an aggressive complement to round out the lower end of the mana curve. Being a card with a double green casting cost, it may limit its playability to Red/Green/X "monsters" decks, but where it does see play it will be a force to be reckoned with.
Having the ability to acquire full-art promotional versions of this card at the Dragons of Tarkir Game Day simply for participating is a great move. Not only is there a great deal of casual appeal to this card, but it should be a solid Constructed card during its time in Standard, as well.