Trample attacks are neither ranged nor melee attacks. So you don't get any Melee +X traits.
Great call, but there is a picture of a sword in a red circle, in between the cool new trample action speed icon, and the 7 dice indicator. Looks exactly like the melee attack indicator on the attack just above. It could mislead a bunch of people, maybe new players, or returning players.
Regardless, super rad card. Warlords everywhere are cheering! Amazing flavor text, possible new meme material. I wish "short-lived success" for all my opponents.
Think of it as similar to Zone Attacks. All Zone Attacks quasi-ranged attacks, but they aren't your normal ranged attacks and have many rules unique to them. They don't benefit from all the same buffs as other ranged attacks, and they have innate benefits and limitations that normal ranged attacks do not.
In the same manner, Trample Attacks are quasi-melee attacks, but they aren't your normal melee attacks and have many rules unique to them. They won't benefit from Melee +X, or indeed anything that specifically benefits melee or ranged attacks. Like Laddin said, they don't actually count as Melee Attacks, despite them being an offshoot of melee attacks and having some things in common. I recommend looking over the full Codex description and rules for Trample whenever it gets released.
@iNano78
Lion Savagery indeed would not give it Piercing.