Do you gamble? Your answer should determine what to do. Most Lenders have a floatdown policy. If you lock now and the market improves by a certain percentage of basis points you should ask for a rate renegotiation. Understand that every Lenders policy is different so ask before you lock.
If anyone claims to be able to answer this question for you they are lying. A person can no more predict what will happen with interest rates any more than they can tell you what 1 share of IBM stock will be selling for at the end of trading tomorrow. Sorry to throw water on your hopes but that is simply the reality of an open market.
There is a little hope for you though if you want to do the work of paying attention to a couple of key items. Here is what you will want to look for, but keep in mind that nobody is able to predict these things with any accuracy; this is unfortunately a decision you will have to feel good about and make on your own.
Unemployment and inflation are huge players in bond rates (which are the basis for mortgage rates), if you see either of these increasing be assured that rates will follow suit because both erode the future return of a fixed rate instrument like a mortgage.
If you are going to watch any one bond, my advice is the 10 year T-Bill. Also keep an eye on the stock market. Another good general rule of thumb is that as the stock market falls, money flows to bonds and therefore improves interest rates. Bad news for the stock market is generally good news for mortgage interest rates.
It's possible that the rate will rise further before October too, and most lenders will lock a rate in for only 30 days. Check with your lender to see what your options may be.