In 2011 & 2012, my Dec SS video sales were below average as compared to the preceding 11 months of each year. Last year, however, Dec was normal and it was Nov that was well below average.
This year, my Nov was well below average, so I'm hoping perhaps 2014 might be a repeat of 2013 as far as Dec is concerned. (I do not look at my sales until the month is completed, so I can't say how my Dec is going.)
I don't believe Bigstock's 50% increase is going to impact sales much, because 45K clips is still very, very small. However, if/when that number grows to 100K or 200K, I'd guess we will start to feel the effects. I don't know what deal they're offering to videographers, but it must be a good one in order for them to accept having their clips practically given away.
I also believe that in many areas, video has already reached saturation level. Too many contributors with too little demand. It was a much faster cycle than with photos, but it was inevitable. Those who specialize in video and really know what they're doing will continue to grow and do well. Those like me, who shoot videos as an adjunct to photos, should be prepared for dwindling sales over time.