Jack just grins because yes, of course it's a suggestion, and a damn fine one at that. And then he's shivering, because Ianto sounds as confident and commanding as he looks and that is hot. It's not something he gets quite as often as he'd like from Ianto (which is one of the things he'd worried about missing when he agreed to the blue bands right at the start) so when he does get it he grabs it with both hands and makes sure he gets the most he can out of Ianto's dominant mood.
"Yes sir!" he quips, rather breathlessly, and after a moment's pause to enjoy the sight of Ianto's hand sliding over that lovely hard cock, he rolls smartly over onto his front and gets his knees under him and spread out, so his ass is lifted and presented to Ianto. He can feel the faint stretch in his well-used hole just from that, and he shivers again at the thought of how it's going to feel by the time Ianto's done with him.