SEV's projected release date is somewhere around Christmas I believe. So, not all months are going to be so sunny. And who knows, perhaps sunshine will be limited this summer?
I suggest, go on with it. Indeed, if SEV turns out to be really buggy at first I think people will play SEIV for some time. Btw, it's great practice for when the game comes out. You'd already have the basic skills and, most importantly, you know how to make your mod playable. You would know how to recognize - and compensate for - grossly imbalancing things.
(However, on the other hand, you might want to create some pretty imbalancing occurences. I mean, look at my Cultures & Demeanors Mod (tucked away somewhere in some faraway page) with its Megalomaniacs and Genocidal Megalomaniacs, with massive bonuses in combat (reaching up to 100%!!!!! for the Genocidal Megalomaniacs I believe) and compare those with the Transcendi and the Pacifists, who both have terribly weak combat. Pacifists have a -80% combat modifier!!!)