Desktop still rules.
In this article by AdAge.com, researches have concluded that Mobile Video spending by marketers will still be overshadowed by desktop video.
Anecdotally, I'd point out that desktop videos look much better, and are arguably a more easily-justified spend. But statistics from Facebook and Youtube conclude that they get far more plays from mobile devices than non-mobile, and 2015 isn't yet half-over.
This speaks to a disconnect between ad-buyers and consumers. From the article:
This year U.S. adults -- not the teens that are already considered glued to their smartphone screens -- will watch 39 minutes of video daily, on average, on their smartphones and tablets. That's the majority of the 76 minutes daily they're expected to spend watching video across all digital devices, which includes internet-connected TVs, desktop computers, tablets and smartphones.
Video marketing is (mistakenly) still in a TV mindset, according to AdAge, and it doesn't look like that will change much in the next 5 years.