On the A320 family, it depends on the FMGS installed.
The FMS2 equipped aircraft will give you single-engine fuel predictions on all phases, down to the primary destination.
On the older ones (Legacy?) you'll lose all fuel prediction, except on the descent phase where it'll revert back to two engine predictions.
On either case, if you push the EO clear prompt two engine predictions will be displayed, and if still single engine, you'l have to check the QRH for predictions.
Safe flights!