As always: it depends. For some workloads something like Citus [1] might allow you stay within the PostgreSQL ecosystem even when you are trying to do OLAP.
1TB is peanuts. You can usually get by even with a lot more. Once that's expired though, you can just switch relatively easily to a different flavor of Postgres.
It's why AWS Redshift exists: Postgres with column-oriented storage.
[1] https://github.com/citusdata/citus