Following features should be added in the CI3.x upcoming versions

1. Modularity Feature
2. Hybrid Oauth easy integration
3. Speed should be increased more
4. Easy available of the UPS,Usps, fedex and DHL APIs, now it is very difficult to implement in the CI.

#2 and 4 are likely to stay in the realm of 3rd party libraries for the foreseeable future (and #4 is definitely not in the realm of most people's idea of a framework).

#1 is debatable for CI4, but probably has little chance of happening in CI3, especially since it's already supported by 3rd party libraries (which will probably be where it stays for CI4).

#3 may happen over time, if people can identify areas which can be improved, but there are limits. Certainly, no one intends to make it slower.

Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide