RC could always move with out the control, he could however be controlled with it. Buzz being hosed down and RC being in the rain shouldn't short them outprovided water doesn't get into their circuitry. Provided they're not submerged in water, it would be like if your phone got a bit wetLast I checked. Still sounds like Potts in the new sneak peek, but as mentioned by @madethistocomment she doesn't sound quite right. I'd chalk that up to age (as Woody and Jessie are sounding a bit older too) and being out of practice with the role after nearly two decades.
Plus the newest clip is supposed to be a flashback, though it raises a few problems regarding one of the characters.
Now we know that batteries, or a lack there of, is not detrimental to a toy that much- Buzz's toy based electronic features are secondary, and the others don't need them at all, but RC's a odd one based off of both this new clip and the first movie. In the latter, he clearly needed them to move around (at least with the controller), and here, since he is a toy whose electronic features make up the whole point of the toy, he's shown in both the rain and moving without the use of the controller. Now I want to say water should short out such features, but seeing as Buzz hosed himself off at the end of the third movie and his voice box function as a regular toy was still working afterwords, I honestly don't know what to say.
Though considering it's literally only 30 seconds long and it's a flashback, this could lead to an explanation as to how RC eventually got removed from the group. But I feel like it's going to raise a lot more questions than answers once the movie actually does come out.