I don't think Open Office factored into Oracle's analysis of the Sun acquisition at all, and I doubt they'd notice if it disappeared. They've got other things on their minds.
There is that alternative implementation, called Apache Harmony, that's like this huge elephant in the room of every JCP vote they have, reminding everybody that the Java standard is in fact a tightly controlled, proprietary farce, having nothing to do with standards that are controlled by real standard bodies (although regrettably, besides Google and Apache, nobody had the balls to vote against the Java 7 roadmap; although the members did express concerns, but for the JCP that's as natural as screaming when taking it in the ass forcefully, without consequences for Oracle)
I do hope somebody will fork Java SE (the standard). If Google gets away with Android, maybe Dalvik will evolve to be a drop-in replacement to Harmony's VM.
Larry must think Microsoft has enough enemies to keep it in check without Oracle having to devote resources to that.