Is this not the correct approach to asynchronous texture loading on Android?
Sorry, apparently I hadn't signed up for notifications, so I didn't realize anyone had answered me. This is all great info. I think I confused the Linux SDK with the Android SDK, and I got worried that there's some issue with EGLImage -- my mistake.
I've tried context sharing before, but I'm under the impression that it isn't universally supported, and I still need to support OpenGL ES 2.0 for now. I'll be looking into PBOs for the future though.
Thanks to everyone for their thoughtful replies.