Not only better hardware but better software too. We are about to enter a period where mobile video will become mainstream. It is already happening on the older social netwrorks.
Why do you think mobile video will become mainstream? A lot of mobile video is hard to watch, and requires a better connection than other mediums. Vine is interesting in that the capture mechanism is interactive,but do you have any examples besides the use of Vine? I'm still unclear whether it will stay or will be a fad -- it's hard to tell due to their awesome distribution.
Faster mobile networks and apps that make it easy to share and fancy-up with filters and whatnot.