The sad truth is that "see you soon" doesn’t mean anything at all. It doesn’t mean he likes you or he doesn’t like you or even that he will see you soon, or he won’t. It is a phrase that ends the conversation as meaningful as "later" or "best". It is a code to show that the message has ended. It might as well be "bye". It has no emotional or practical significance whatsoever. In that context, the true indicator of a guy’s feelings is not what formula he chooses to close his letters with, but the fact that he hasn’t called or emailed you. Men don’t really require such fine analysis. You’ll know it when a guy is asking you out, for instance. He will do it like "Would you like to have dinner with me?" or "You wanna grab a bite?" depending on who you choose to hang out with. This is as multi-layered as it gets with a half decent guy.
Human beings are obsessed with alleged reasons and pretext because such concepts provides them with means that could be comfortably and incorrectly perceived as wisdom or quality sense of judgment. The fact, however, is that alleged reasons remain to be as valid as prestidigitation or cold-reading!