Short answer: The CHT is absolutely suitable for a deployment of this size! There are currently a number of existing deployments with 1000+ users and the soon-to-be-released next generation architecture in version 4.0.0 will allow the CHT to support a much larger number of users!
That being said, any kind of software deployment with 1000+ users is a significant undertaking and a CHT instance at that scale would be no different. Having sufficient server resources (CouchDB users a lot of disk space and RAM) and the proper configurations would be essential for making sure the system remains performant.