Well, if you saw their recent video for their Falcon Heavy plans (see here if you haven't, it's pretty dang cool:
https://www.youtube.com/watch?v=u26-CIDaazQ ), you may have noticed the landing pads. Just today, they announced that facility they're going to lease to put that together:
http://spacenews.com/spacex-leases-cape-canaveral-launch-pad-for-falcon-landings/SpaceX’s plan calls for constructing a 60-meter by 60-meter square concrete landing pad surrounded by four additional 45-meter diameter “contingency” pads, according to a 2014 environmental impact statement prepared for SpaceX and the Air Force.
“The contingency pads would only be utilized in order to enable the safe landing of a single vehicle should last-second navigation and landing diversion be required. There are no plans to utilize the contingency pads in order to enable landing multiple stages”
So by the sounds of it, they do plan on a flyback eventually, but that would be a ways off yet, since they're just acquiring the pad site. Could also depend on the launch trajectories; this launch was supposedly coming back down under more extreme circumstances than their ISS missions due to the target being deep space. Seems likely they just tack it on as a checkbox on the order form. "Does your mission need a little extra delta-V? Choose this option a pay some extra for an at-sea booster recovery."
Moreover, they have a second drone ship under construction for the West Coast (named "Of Course I Still Love You"), which would imply this isn't just a temporary thing. Interestingly, I can't seem to see any info about any currently active SpaceX launch sites in the Pacific, having shuttered and dismantled their early Omelek launch site there. This would seem to imply the drone ships may not be just for the first stage boosters, but rather intended in the long term to be used by capsules re-entering from space... Those do regularly splashdown in the Pacific, and they do have plans for flyback recovery of the Dragon V2 capsules, so I would expect to see some testing of those landing on the droneships in the next few years...
There had also been some mention about potentially having automated refueling on the droneships, for a second flyback from the ship to land? (I guess?), but there aren't really any details on that yet. It may well be they decide to go all out bonkers with it and have them land on the barge, refuel, then fly back to land, which would be pretty badass, though I think that may be a logistical nightmare. So we'll see.