I would launder it and wait to see how much shrinkage you get. Shrinkage depends quite a bit on how each person cares for their shirt. Looks like that's a charcoal heavy oxford? If so, I'd wait to change size until you've washed it 2 times. Those shrink quite a bit in comparison to most of the styles we carry.
For those with arm tightness issues--we're currently in the process of prototyping a 3 pleat forearm. It won't help if you find the armpit too tight. But you feel like you could go slimmer in the bicep, but worry about the forearm becoming too snug, then give it a try in a month or two when it's ready.