I've used the GoPro since the model Hero HD, then the Hero 2, Hero 3 Black Edition, and Hero 3+ Black Edition. It seems like there's give and take with each higher-spec, newer model.
Although the Hero HD and Hero 2 took the same size battery, batteries always lasted a lot longer on Hero HD, plus the Hero HD does not heat up as quickly as do Hero 2 and 3 series. However, the HD's optical sharpness was weaker at distant subjects--even when set to the same resolution settings as the Heros 2 and 3.
Regarding the next Hero models, it would make sense for GoPro to introduce a Hero 4 with higher frame rates. However, they need to overcome the varied write performance of microSD cards. In fact, their firmware update to the Hero 3 will automatically reduce the frame rate when needed.
This is but mere speculation...the other new GoPro model would be the model 360--that would shoot 360-degree video and stills. Some companies have built prototypes or rigs for this purpose, some of which use GoPro cameras, but it needs much stronger hardware and software support, such as that which GoPro could provide. Typically, a 360-degree camera would employ at least 2 or 3 lenses and sensors. The still shot-only Ricoh Theta camera is an example of a two-lens 360-degree camera: one lens points fore and the other points aft. The Geonaute is a three-lens video camera (not yet released).