Richard Young notes: "the basic syntactic function of KAI is simply to join two coordinate elements together" (187). But KAI can also be used as a simple additive without specifying any particular relationship between two coordinate elements (see Rev. 7:12). After looking at the various uses of KAI in the NT, it seems that the KAI in 2 Cor. 5:8 is best understood as a simple additive that connects two contrasting thoughts without specifying the temporal aspect of either one. 2 Cor. 5:8 is an expressed desire, not a prophecy per se.
One of the best discussions I've run across on the utilization of KAI in the NT is Kermit Titrud's "The function of KAI in the Greek New Testament and an Application to 2 Peter" found in D.A. Black's Linguistics and NT Interpretation: Essays on Discourse Analysis. His paper will expose you to the numerous aspects of the Greek conjunction KAI.