I'm hopeful about mindfulness-based treatments for a few reasons. For one thing, more people meditating is generally a good thing. These programs do incorporate many (but not all) aspects of the Dhamma, like not clinging, disidentifying from thoughts, emotions, and sensations (which is a precursor to anatta). A person who does this regularly enough is not guaranteed but more likely to discover many core Buddhist principles. For example, some studies show that when people are just given mindfulness training, it also increases their compassion, even though that was not specifically taught.
A second reason is that a percentage of people who take to this practice are going to look further and will likely look deeper into Buddhism, knowing that that's where mindfulness-based treatments originate. So when thousands upon thousands of people are exposed to this therapy, that's many people who may not have otherwise found their way to Buddhism. Researchers in this field are churning out research to the point where this is taken seriously now, rather than seeming like some new-agey fringe nonsense.
A third point is that many of the researchers and clinicians who do mindfulness based treatment are also Dhamma practitioners. This is an evolving field, so my impression is that people are gradually explicitly incorporating other aspects of the Dhamma as they figure out ways to work them in. For example Paul Gilbert developed Compassion-Focused Therapy. Acceptance and Commitment Therapy is strongly based on emptiness. These psychologists have made a first attempt at incorporating sila into mindfulness therapies:
This article by Shauna Shapiro & B. Allan Wallace integrates many aspects of the Dhamma with contemporary research. It was published in American Psychologist, which is probably the most prestigious psychology journal in the USA:
So no, mindfulness-based therapies are not the full Dhamma.But it's going to be interesting to see how all this progresses.