It's still too soon to say, but it certainly doesn't look good. A good defense attorney will rape and pillage a witness for a change in testimony, so he better have a really good story as to why he changed up. At that point it just comes down to whether or not the jury finds him credible.
I would be equally concerned at this point in not having the murder weapon. Also the fact that there's been so many new indictments lately could possibly indicate that the prosecution is trying to drum up a more credible witness.
Who knows. Like I said, it's still early.