Parker may get squeezed out by numbers. Right now, Veras, Strop, Wright, Russell, and Villanueva are guaranteed spots. Cabrera is out of options, so that may help him. That leaves at least 3-4 guys who they'd like to carry for 1 spot (maybe 2 if they don't carry Cabrera): Parker, Grimm, Rusin, and Rondon at least; maybe McDonald, Rosscup, and another non-roster guy or two. So I could see how he'd get pushed out.
I agree that he should be a lock, though. I expect he'll make it--right now, it looks likely that Arrieta won't be ready for the season, so that will put Villanueva or Rusin in the 5th starter's spot. I think we'll probably see at least one or two of the Villanueva/Russell/Cabrera group traded by the beginning of the season too.