Lately Sony has been holding out on the US and Europe. Why do I say that? Well an invitation from Sony says “Join us for an introduction to the slimmest. The biggest launch in PlayStation history”. The most “sensible” option that IGN points out would be the PS Vita Slim. The reason this is the most likely candidate to be launched is probably because of the PS4’s remote play option, utilizing the PS Vita Slim.
The PS Vita Slim is already about 20% thinner and already available in Japan. It makes sense that Sony would also want to release it here, in the US, and in Europe. Everyone wants the latest and smallest it seems, reasonably being the purpose Sony has for releasing the 15% lighter PS Vita Slim.
The Slim has a 5-inch LCD Display that they claim helps battery life for the PS. In Japan the Slim comes in 6 colors, possibly the same as in the US and Europe. The Slim in Asia/Japan is about ¥18,980, the equivalent to $190 in the US and €140 in Europe. There hasn’t been confirmation about this assumption, but all evidence points to this conclusion.