Unit Explanations: Fiddling with Phoenixes

Unit Explanations: Fiddling with Phoenixes 

Image from: http://starcraft.wikia.com/wiki/Phoenix

The Phoenix is a very versatile unit that (in most situations) can help swing a battle your way. You would think being only able to attack air would stop them, but your wrong. They have a mass of locked potential that is destined to be found by you.

Starcraft News

New Heart of the Swarm Units

Image Found at Starcraft's Official Facebook Page

So it seems silhouettes of the new Starcraft 2 units have been released; what could these units be? These units really do have a sense of mystery about them as we really do not know how they will affect our games. The above Zerg unit looks to me as if it is a Zergling with a hard shell on its back. Could this be some sort of new armoured unit?