While (apparently) there is no provision with SARP or PANS status which explicitly prescribes runway vacation without further instruction, there is 7.10.3 of PANS-ATM, which says:
When necessary or desirable in order to expedite traffic, a landing aircraft may be requested to: [...] c) vacate the runway at a specified exit taxiway
In my opinion, it follows from this that, when such a "request" is not made, landing aircraft are permitted and expected to vacate the runway at the first suitable taxiway, i.e. one which has not been "specified" by the aerodrome control tower.
Apart from SARPS and PANS, there is also Appendix B to the Manual on the Prevention of Runway Incursions (Doc 9870), where it says in 6.3.12:
After landing, the runway should be vacated as soon as possible, but not by turning onto another runway, unless specifically instructed to do so. When the aircraft has vacated the active runway, the pilot should be prepared to stop to resolve any questions about the ATC clearance or about the aircraft position.
Needless to say, the Technical Manuals do not constitute SARPS or PANS, nevertheless they are published to facilitate the implementation of the former.