I can't imagine that they will get much bigger relative to the rest of the computer than the 13" already is. It would just be nice to be able to scroll further, do gestures easier, etc. Similar to the magic trackpad, I assume
They serve as another reason why I buy Apple laptops, because I hate PC laptops with their tiny little trackpads and their stupid-ass left and right buttons. Not to mention that a PC trackpad is NOT centered on the palmrest; which is stupid beyond words.
I've had my MBP for over 3 years of solid, constant work (and play!) and have YET to have my palm accidentally click on something or move the cursor in any way. I use the trackpad 99% of the time, I only use my bluetooth Logitech mouse when I play vidyagames.