Sean,
What do you mean by "the PCA … is soon following their footsteps"? Has the PCA abandoned the gospel? Are their talks within that body that they will be doing this soon?
The term Presbyterian does not imply full assent to Calvin's theology. In fact, I know of few churches that would subscribe at all points to his doctrine. It deals with polity. And while historically derived from the teachings of Calvin (and others), it does not need to adhere to (all/many of) his teachings.
Willis, there are many different presbyterian bodies. Greg and Sean, for example, have mentioned two different ones with differing histories and beliefs. To which denomination does she belong? Sadly, many denominations hold the Westminster standards rather lightly with regard to certain sections. The PCA largely ignores the confessional understanding of the 2nd and 4th commandment, for example. Recreational exceptions to the 4th commandment seem to be quite common in the OPC. Moreover, Exclusive Psalmody, which WCF 21 confesses, is not to be found amongst nearly all OPC churches.
Presbyterians aren't as uniform in their doctrinal understandings. Most, de jure, however, are governed by elders. Hence the term.