Late last year and early this year, I used a number of upgrades to ride Acela First Class. As far as menu rotation, it didn't 'rotate' at all over a period of 5-6 weeks. Then, surprise, surprise, it changed!
If you have the luxury of not eating as soon as you get on (which the on board staff apparently wants you to do), wait until a couple of stops have passed so you can get a look at the choices others made before you order.