The answer maybe is we already are two consciousnesses, or maybe more. Look at the fig. 1 here, that deals with an experminent on someone with a split brain, a hemispherectomy: http://www.cisi.unito.it/neuropsicologia/didattica/materiali/approfondimenti/attenzione/2003/gazzaniga.pdf
it should be noted that consciousness is a phenomenon that science still knows little about.
source and further reading:
http://www.reddit.com/r/askscience/comments/iee9g/if_you_become_a_splitbrain_patient_which_side/c235ow4