Given that there appears to be very little solder on the power switch, is that something that may need work in the future as well?

Unlikely. Those joints look fine, and in any case it's normally either very fine pitch or stressed joints that are prone to failure. For cost reasons, the art of SMT manufacture is to get the amount of solder paste used down to absolute minimum, while still having sufficient to do the job reliably. It looks like your unit is pretty close to the limit That said, it's unlikely that there would have been a problem, unless the connector wasn't quite up to spec as well. An unfortunalte coincidence, probably. There could also have been a little contamination on the pcb before it was reflowed, and if so this would be a local problem, rather than pcb-wide.

Is there anything else that can or should be done to prevent future problems?

Not really. Occasional dry joints are a fact of life, especially with fine pitch smt equipment, and cars are a high vibration environment which exacerbate the problem. The pcb is very well fixed into the case, which is also very rigid, so board flexure is most unlikely to cause failure, but sudden shocks and major temperature cycling is never a good idea and should be avoided if possible. However, even with all this, it's much more likely that the HD or display would fail first and even that possiblilty is low.

pca