It was only a pre-order incentive before
Now that Sniper Elite 3's been out for a few weeks, anyone that's developed an adequately itchy trigger finger can set their crosshairs on a significantly more prominent figure. Adolf Hitler's the target this time, and he's kind of the glue to that whole Axis of Evil thing.
The real dedicated marksmen could've set out on their mission significantly earlier. The Hunt the Grey Wolf DLC was available for free from the get-go to those that pre-ordered the game. Now, the more cautious snipers can buy it for $8 on consoles or $10 on PC. That seems like a reasonable price to become a worldwide historical hero.