Having used the lockers at both Forbidden Journey and Gringott's (and the traffic jam/lack of availability), I can see this being a real issue, especially since Disney has fastpass with a schedule time, as opposed to Universal's express pass (which, btw, isn't available for Forbidden Journey or Gringott's). Unless Disney carefully thinks through the process, I can see upset guests who may miss their FP+ window as they scramble for the few available lockers.
We have a zip lock bag in our backpacks for our phones and cameras for rides like Kali and Splash. Once again, if a guest doesn't consider how wet Kali is (stand on the bridge and observe the ride) and plan accordingly to protect their electronic/digital devices - why is that Disney's (and subsequently ours) problem? Install a BIG sign that says, "You WILL get wet on this ride" and hand out plastic bags for those who want them. And then have a CM at the exit whose sole purpose is to throw in the trash all the plastic bags people will drop on the ground as they leave. Oh, wait, I forgot, this is Animal Kingdom, so they probably won't hand out plastic bags. Oh, well. Bring your own.
BTW, not all the lockers at Universal are free - only those at rides where you are forced to put your stuff in a locker....