Yes, it is possible.  It is  stated that despite extractions, as long as you maintain proper oral posture, you can prevent any kind of damage to the arch shape or the general face shape.

V-shaped palates are a result of poor oral posture?

pretty much.  tongue isn't pushing the upper teeth apart so over time they come together

V shaped palates happen when the vault loses support .The teeth become crowded and the intermolar width narrow. Result of poor oral posture

This is interesting. So it is correctable over time?

Is it always preferable/worthwhile retaining wisdom teeth? I'm having trouble with one of mine and wondering if I should just get it removed or put up with occasional pains,etc. until they can be dragged forward with braces.

I think when it comes to ideal facial development, you're gonna want every tooth you can get your hands on

Mewing should correct this over time. A study done showed that an average of 3.2 mm widening between maxilla canines is normal within 8 months of mewing as an adult. Depending on the state of one's specific situation more is possible. 2 Years should yield around 5 to 6 mm as well as proper jaw alignment.

As ppl near correct structure over time the process slows down and eventually stops when correction is achieved. Time needed can be anything between 1.6 years to 10 years depending on the individual case and how efficiently one is mewing.