^ The article seemed to think he did have an input.
I'd also expect that he would. In DH3, he brought along Jackson, his Pulp Fiction co-star, while he was also supposed to have nixed David Thewlis as the baddie for that movie. The studio wanted Thewlis, after his award winning turn in Naked (he also looks more like Rickman than Jeremy Irons) but Willis insisted on a name actor, and got his way, with Oscar winner Irons joining the crew.
Willis also got on well with Ben Affleck on Armageddon and for a long time, Affleck was supposed to be joining the set of the fourth DH movie as Bruce's son/sidekick.
So, you could be onto something, if Hemsworth and Willis get on on the set of The Expendables, he's likely to land the role.