If this thing comes to fruition it will be a relative seniority merge +/- 1-2% just like DL/NW, AW/USair.
Both airlines are hurting financially just one (UAL) is happening sooner, but CAL's time will come next year if things do not turn around. I am a CAL guy and our finances next year do not give me a warm fuzzy, and if this happens we as pilots will have to get together and make sure we are compensated very well for this merger.