If you are currently processing integrated payments through Moneris, Tyro or Cayan and have a perpetual contract, nothing about your workflow should change past End of Life.
As of OnSite 2019.2, no other payment gateways are supported for OnSite. If you wish to update to the latest version of OnSite, you will need to switch to Cayan or Moneris to continue offering integrated payments, either directly through them or by using Cayan as a gateway for select processors. If you wish to use unsupported payment processors, your payments workflow will change to be unintegrated.