I think we'll eventually wind up with a hybrid solution: really vital/frequently accessed data on wearable devices (thumb drives, SD cards, etc) and personal clouds: basically people accessing external drives at home via internet, rather than relying on someone else for cloud service. It requires a static IP address in most cases, but the fee's nominal (I think my ISP is $4/month) but it means I've got my own 2TB cloud, in addition to the 128GB card in my AirStash (which, tbh, is mostly videos and photos). Most personal cloud set-ups now come with Android/iOS apps to make them tablet/phone friendly as well.
I think hybrid solutions will continue as well.
For now, my husband has set up so we can stream some of our media from an NAS server, but I've not used it much outside of home. For when I want some extra movies away from home, I'm more likely to use SD cards with non-Apple devices, so that I don't need a connection.
I considered getting a Seagate portable hard drive when iPad first came about, but didn't like what I read and decided against adding to my load and charging routine. I might get one eventually if really needed. Meanwhile, I have a 3TB portable hard drive that's pretty small and light, which I sometimes bring from main home to vacation home, because we have laptops at both, but usually don't bother with.