Seems like people are forgetting some things about the merger.
1. This merger has and always had a very high probability of happening, considering that the same person pretty much founded and runs both companies involved, and they have been operating as one in many ways for years.
2. Unless you think SCTY really is so desperate that it needs a bailout, Tesla is getting a really good deal on SCTY. It's a lot less expensive for Tesla to acquire SCTY when it looks like damaged goods than when SCTY is flying high. Musk & Rive are not ignorant of this.
3. Building companies and building stock prices can be two different things sometimes. I don't know if it will be a month, a year, or five years before this becomes the accepted as fact, but solar + batteries pretty much makes more sense than any other form of power generation right now. Tesla does batteries, SolarCity does solar. Put batteries and solar together and you have a product that pretty much sells itself, kind of like Tesla cars.
4. I think we're getting to the point where people (and analysts) are close to accepting that Tesla is not just a car company. It is constantly reinventing itself and adapting to changing climates and opportunities. SCTY is just another part of that adaptation. If you want to worry about something, start to worry when they've gone a year or two without doing something that makes your scratch your head.