How to know the version of iBus I'm using?

You can run the command ibus version to see which version you are running. I'm still personally trying to figure out how to update it myself

edit: I found a post that breaks down installing the newest version of ibus, link.

Also in case you run into the same error I did when attempting to install it, if you run into the error saying your intltool is too old run:

sudo apt-get install intltool

When you run the make command stated in the above link, you might get a lot of missing packages. For the most part just install them one by one and if need be google to find the source package for some.

The version of iBus or any package that you are using is normally found using apt-cache policy package where "package" is the name of the package that the software belongs to. In the case of iBus the package is called "ibus":

➜  ~ apt-cache policy ibus
ibus:
  Installed: (none)
  Candidate: 1.5.11-1
  Version table:
     1.5.11-1 500
        500 http://httpredir.debian.org/debian testing/main amd64 Packages
        500 http://httpredir.debian.org/debian unstable/main amd64 Packages

In my system, there's no iBus installed, but if I were to install it, I would get the 1.5.11 version. You can figure out which version is available for any release of Ubuntu using madison:

 ibus | 1.4.1-3ubuntu1   | precise        | source, amd64, armel, armhf, i386, powerpc
 ibus | 1.5.5-1ubuntu3   | trusty         | source, amd64, arm64, armhf, i386, powerpc, ppc64el
 ibus | 1.5.5-1ubuntu3.2 | trusty-updates | source, amd64, arm64, armhf, i386, powerpc, ppc64el
 ibus | 1.5.9-1ubuntu3   | vivid          | source, amd64, arm64, armhf, i386, powerpc, ppc64el
 ibus | 1.5.10-1ubuntu1  | wily           | source, amd64, arm64, armhf, i386, powerpc, ppc64el
 ibus | 1.5.11-1ubuntu2  | xenial         | source, amd64, arm64, armhf, i386, powerpc, ppc64el, s390x
 ibus | 1.5.11-1ubuntu3  | yakkety        | source, amd64, arm64, armhf, i386, powerpc, ppc64el, s390x

If you want a release of Ubuntu that includes 1.5.11 or later, I recommend using xenial or later.