Are the existing payment symbols (variable, specific, constant) going to stay in use after the 30.1.2016?

Yes. In case of one-off payments, the payer will be able to fill in the payment symbols as up to now. Both payer and recipient will process these information from the SEPA XML statement (CAMT.053) from EndToEndId.

In case of the payment file pain.001 or debit file pain.008, using the agreed payment symbol convention in the EndToEndId (payer`s reference) is mandatory: /VS0123456789/SS0123456789/KS0123