You have absolutely no right to evict your tenants because they won't sign a new lease. Damages awarded to tenants for illegal eviction are usually either 4 or 5 figure sums - excluding cents!
Once a tenant has been living in a property for six months, the automatically acquire the right to remain in the property for a total of 4 years without signing a new lease.
However, the type of tenancy that they now have is called a Part 4 tenancy and it is not as secure as having a fixed term lease because the landlord has 6 options or grounds on which he may terminate a Part 4 tenancy, whereas, with a fixed term lease, the landlord may only terminate if the tenant is in breach of the terms and conditions of the lease or there is a suitable break clause.
It is the tenants' choice to decide if they want to remain on a Part 4 tenancy for to go for another more secure Fixed Term lease.
I respectfully suggest that you google "Residential Tenancies Act 2004" and download a copy (available in pdf format, and read section 34, "grounds for termination of a Part 4 tenancy". Also available on the PRTB website (last time I looked).
Sections 19 to 24 cover rent reviews.
I assume that you have the tenancy registered with the PRTB.