I think you answered it yourself, there is no definitive answer since the product is not out yet but the consensus is the increased speed is the result of a new chipset.
The new phone probably won't be out until June maybe later, so if you can wait till then by all means, if not, then get one now. I bought my iphone last december and I've not regretted it once. I realize a faster more feature filled upgrade is due, but that's the case with any technological device. The current iPhone exceeded my expectations and far surpassed my needs.
bottom line, if you need one now, get it now, and enjoy it, if not hold off for a few months and get the updated unit