Redis is such a well-written C software that I can't help but think modules might become an antipattern to Redis. I like the idea that the option to use modules exists, but I hope it doesn't spiral into dependency hell as it is with the Ruby ecosystem. I hope library developers think very hard before employing and requiring a module.
Redis is fast, easy to use, and extremely flexible, and makes it easy to use any of the hosted options (Redis Labs, RedisToGo). Its allure is that Redis is batteries-included yet small enough like a Swiss knife. I wouldn't mind installing a module if it brought in significant optimization for a specific use case. I personally hope most library developers will pretend modules don't exist, and that only app developers will use them. I have this selfish desire that most libraries stick to the vanilla Redis features, because for most things you can use app code to manipulate the features you need without modifying Redis and compromising performance. Modules might add to the heap of things to think about, such as special Redis deployments or the things that can go wrong with the module code.
My fear is that instead of years of using the simple Lego blocks that is vanilla Redis, modules will start a pattern where we need to install special modules to use certain libraries.
TL;DR, I'm worried for the potential for abuse with Redis modules. My love for Redis was how simple and powerful it is, and yet now Redis has grown up, ready for modules.