More than likely to be renumbered - 7626 has likewise been renumbered in Yorkshire before entry into service (as their 1551).
Reports on the 'Travel West Yorkshire' Forum confirmed the other pair of Geminis moving to Yorkshire are 7618/9 (likely to become 1549/50) in exchange for Yorkshire's 1917/8 (SN15 LLF/G).
RE: Arriva North East: Latest News & Discussion - September 2018