I'm confused... Aren't Presbyterians Calvinist? I voted no to all predestination questions and ranked them with high priority. 
Most of the mainline churches pay little attention to their historical theology.
It really feels like a merger ought to be in order for some of these mainline churches. It seems like your standard PCUSA church isn't far different from your average UCC church (which itself was originally a Reformed church anyway). I think the biggest dividing line between mainliners and liberals now is church polity and worship style, with folks like Madeline and myself favoring high-church atmospheres with at least some form of hierarchy and BRTD-types going for the autonomous low-church style.
There's on again off again speculation of a realignment in American Presbyterianism since there are roughly four to five 'parties' and over dozen denominations plus microdenominations. Typically one or both of the following are speculated to happen:
1) PCUSA loses conservative churches to the evangelical denominations while merging into a mainline 'supergroup'
2) The PCA splits between broad evangelicals on the left and confessionalists on the right and join up with the denominations to their left (EPC, ECO) and right (ARP, OPC, CREC),
