I was quite excited when it was first announced, but it's more of an iteration than a new camera. If it was my first Ricoh GR, then sure, because it will be better than the GRIII, but as an upgrade, no thanks.
The main issues I have with my GRIII are the reflectivity of the fixed LCD screen, which can make it difficult / impossible to see in certain light / angles, and the battery life (although I carry several batteries, so not a major problem). I'd have loved to see weather sealing, a tilting LCD, and a pop-up viewfinder in a new GR (although I appreciate that those would all likely affect one of it's main features, namely the extremely compact design).