It is not possible to install the Jive client on the Nexus 7 I have not tried to establish whether the limitation is the version of Android or the form-factor. In theory a tablet version of the client could benefit from the extra screen space, for example using it to see the previous comments while replying.
I understand that the existing Android client does not work with the Nexus 7 and I would agree with you that the additional screen size does provide an opportunity to provide a better experience. My suggestion is to grasp the situation now, get a 7" Android format version done now and be ready for the iPad mini.
I am working with an organisation that is reviewing the use of the Google Nexus 7 and was fortunate to use a unit last weekend. This product has exceptional capability and the format is getting a lot of very positive feedback.
The N7 uses Android Jellybean 4.1.1 and I would like to demonstrate mobile and would like to find out what is involved in upgrading the current Android app to the new 7” format. I understand that there is a push by Apple to this format with a rumoured iPad mini.