Tinnitus has been reported as a good(Danino et al., 1984), bad(Ben-David et al., 2002), and neutral(Chang et al., 2005) prognostic factor in various studies.
References: Singh A, Kumar Irugu DV. Sudden sensorineural hearing loss – A contemporary review of management issues. J Otol. 2020 Jun;15(2):67-73. doi: 10.1016/j.joto.2019.07.001. Epub 2019 Jul 30. PMID: 32440269; PMCID: PMC7231990.