I'm not sure how much they
will change, but I imagine they'd at least update those pop-culture moments you mentioned. It will probably come down to cost, though; is Scholastic willing to pay someone to go through the books, and find all these comments?
I think you're right about cell phones. The most interesting part of the "Ask K. A. Applegate" thread, to me, was their comment about smartphones changing some plot points. I don't know...any edits could say that the Animorphs are still considered too young to have their own phones, but I know that Cassie had one for emergencies - and geez, I don't know what teenagers are like with phones!

It's probably a pretty flimsy excuse.
They would also have to change how the books approach the internet. Sure, Jake uses a chatroom, and Rachel scopes out Jeremy Jason McCole, but their whole method is relying on Ax and Marco for anything substantial. I know six-year-olds with more computer knowledge than that. They'd definitely have to have Melissa on Facebook, and have Marco make a few cracks about Farmville or something (Oh god, do people still play that?). I'd
really like to see them have some kind of code phrases with Erek through Twitter.
For goodness' sake, doesn't Jake have a Sega Genesis? Or was that Marco?
food/outlet references such as taco bell, radio shack and cinnabon i dont really knwo about, because there are none no outlets with those names where i am from. are they real existing places in america?
Taco Bell is real, but I believe that RadioShack has changed their name. I've
heard of Cinnabon, but I don't have any around. I'm pretty sure they're real.
...Oh, no, I just had a thought. What are they going to do with Jeremy Jason McCole? I mean, JTT isn't a big name, anymore. Are they going to replace him with Justin Bieber?