If you look to the Military Technology Exhibitions that are held about twice a year you get a few indications of where tech is going as most things are utilised for military purposes before they go to market.
A few years back I tried on a full face helmet that allows you to see 360 degrees...
I think the phone's future depends on other things in our day to day lives progressing and companies inventing tech that interacts with and supports these advances. Things we won't see coming I'm sure.
The only other way I can see it going is if they become self-aware then I believe the time machine will eclipse the mobile phone in the technology race.
I don't think much about their appearance will change now. There are bound to be variations such as bendy screens but people like their screens fairly large so I doubt they'll get smaller and any larger they just become impractical to carry about. I think the changes will come in functions and...