That is not really the precedent it sets, though. As far as I can see, the two precedents set are that:
(1) Evidence related to wider offences than those that were prosecuted and led to a conviction ought, be rights, to be taken into account where available, and
(2) Parole Board decisions can't be held as utterly secret, and that the current Rule (25) needs to change so that access is available where it's in the public interest.
This therefore won't, as a matter of course, lead to longer time spent behind bars, except where the wider evidence considered utterly destroys a case for early release, which might otherwise have been accepted. This will, I suggest, be a rarity.
Not that I am sad to see the decision, by any means; having read the judgement carefully it seems clear that there are undertones from the judges that they are amazed at the Parole Board's original decision, and I'm inclined to trust their reading of the evidence. At Paragraph 125 they state:
"With respect, it does not seem to us that this possibility [that Worboys was not open and honest about his recent admission of guilt] was thoroughly probed by the independent psychologists..."
Perhaps it's a product of watching too much Yes Minister, but it's hard to read that as anything other than a polite way of saying: "Seriously? You *believed* this tisspit?!"
Still, apart from that, on balance the judges are wary of trying to decide whether the decision to release Worboys is wrong on principle, rather than wrong as a matter of law. Hopefully, a fresh Parole Hearing will come to a different conclusion, for the time being at least, but there is no precedent set for longer sentences that I can see.