pito:
that being said.. 'is' moving toward +3.3v based boards the trend? (future?)..
Yes.
Oo-er. That's perhaps overstating it. Fast processors have used lower voltages for many years, and even 3.3V is rather high for a modern chip.
But 5V still has plenty of advantages in an Arduino. Minimalist boards based on the 32U4 chip can run off 5V USB power without a regulator. Many components require 5V or run better at 5V: audio amplifiers, buzzers, large LED displays, power transistors, relays...