No. Revalidation is required to maintain a licence to practise in the UK. It is not required to maintain specialist or GMC registration. 

In some situations (e.g. working abroad) you may wish to relinquish your licence to practise (and therefore not revalidate), but remain registered with the GMC and maintain your entry in the specialist register. This provides confirmation that your qualifications have been recognised and that they are in good standing with the GMC. Licences can be reinstated if circumstances change. 

The specialist register records the specialties in which you have trained. If you no longer work in the specialty for which you were originally listed on the register you will not lose your registration if your revalidation is based on supporting information from practice in another field. Revalidation is about demonstrating that you are up to date and fit to practice in your current fields and scope of work.

As a specialist, you will need to continue to meet the existing requirements and this will be evident through the detail of the supporting information that you provide at appraisal. The Royal College of Physicians of London has produced physician specialty resource guides for revalidation which are available from their website.