Texans will get a 3rd round comp pick for Honeybadger so they may have felt they were playing with house money. Texans are also projected to have the most cap space in the league next year (although ~$20M of it will probably go to resigning Clowney, it would still leave them among the highest teams in remaining cap space) so they could just as easily grab another FA RB or extend Miller for 1 or 2 more years. They were linked to Gordon when he was a rookie in the draft so that's an outside possibility as well.
With no GM currently, it's pretty hard to say with much certainty what they will do next offseason or what their current motivations are outside of maybe the obvious: they cut Foreman, they had no one else at the position besides UDFA's and Miller, they have needed a receiving back for a long time, their WR's outside of Hopkins can't stay healthy, Duke is an outstanding receiving back.
With no GM currently, it's pretty hard to say with much certainty what they will do next offseason or what their current motivations are outside of maybe the obvious: they cut Foreman, they had no one else at the position besides UDFA's and Miller, they have needed a receiving back for a long time, their WR's outside of Hopkins can't stay healthy, Duke is an outstanding receiving back.