Either way that's 4 months. Just get an iP4 and sell it when the time comes. I bought my iP4 3 months ago, on the assumption the iP5 may come out in July. Now we're looking at september? I'm glad I didn't wait, and I don't think you should either.
Apple devices usually hold their value. Find one on Craigslist if need be but I wouldn't settle for a crappy phone for 4 months just for something that may come out in september or next year. Get the iP4 and don't look back, if you have the cash.