Most likely, the Board will supplement its findings of obviousness in its Final Written Decision without changing its original conclusions. On the other hand, if the petitioner’s record doesn’t provide the underlying factual findings that the Board will need for this effort, all bets are off.
Strategy tip: Support every obviousness argument in your petition with as many underlying rationales and facts as possible. Even when (and perhaps, particularly when) the combination just seems so obvious. The Federal Circuit is watching.