Separate. Renewals belong in their own funnel with their own stages, because they have a different owner, a different close-date logic and a different set of risks. Reporting new business and renewals through one pipeline makes both numbers uninterpretable.
When an expansion coincides with a renewal, run two records: an expansion deal in the new-business funnel and a renewal deal in the renewal funnel, then merge the line items at close so the contract ends up whole. That keeps bookings attribution honest without misrepresenting the contract.
Every claim above comes from work LeanScale published. These are the sources.