In a musical I played in recently the highest notes that we had written was a high C or high D, which is about my current range. I was annoyed at how I thought they were trying to kill us but a friend said that was typical for some musicals. I think playing higher will be like wanting to bench press 300lbs... sure it can be done but it won't be done by trying to lift 295... it will be done by weeks, months, years of working, challenging yourself to go higher and then eventually getting to that goal.
A guy I'm working with said that if you want to play high, then do it. e.g. practice playing higher or do exercises that challenge your upper range. Arguing about it on this post will never increase your stamina, abilities, etc. However if your highest note is "X" and today you try to play half a step higher you may or may not be able to but if you keep working on it you will get it (and if you can't then get lessons or someone knowledgeable to help you with your technique) and once you get there work on the next step.
And I also agree with hitting the note while the moon is aligned with the sun doesn't count as much as being able to hit the note and hold it for a whole note or playing it within a piece of music.