I'm speaking for myself and what I think, rather than on behalf or Postgres or any company. I assume you are also referring to the possibility of a private fork.
What I've seen in the Postgres community is a group of developers that takes an aggressive stance against companies "taking advantage" of the developer community. Companies that invest both time and money in development get far more attention for their patches than companies that try to either throw code over the fence, or do "drive by" development projects.
Tom deciding to take this job indicates to me that it is because Salesforce is making a significant investment in open source Postgres.
to add a small thing to what Selena already said, Salesforce is sponsoring the "Unconference" day at PgCon 2013 (held in Ottawa this week). It could be nothing but it seems to me a good thing.
Despite of that, I think that if Salesforce will let Tom to focus on postgresql development as RedHat did in the past we(1) are ok.
