The 18-year-old keeper began training with the Blues in December, subsequently earning game time for the Academy and reserves.
Seymour’s talent has impressed Kenny Jackett and goalkeeping coach John Keeley, prompting the club to seek his addition to the goalkeeping ranks.
However, the intervention of coronavirus and subsequent suspension of the season has delayed the paperwork.
Regardless, Jackett is keen to sign up Lewes player on third-year scholar terms – ensuring he will serve as the Blues’ fourth goalkeeper next season.
Pompey’s boss said: ‘Taylor has been under the Academy banner and will continue to be next season. That is the plan.
‘He can still play for the youth team and, if we can, perhaps during the course of the year we get him some loans into men’s football. That would be a good thing as well.
‘Taylor will be joining us as a third-year scholar.’
The University of Notre Dame graduate arrived at Fratton Park for a trial at the turn of the year, staying with his Fareham-based grandparents.
Measuring at 6ft 7in, Turnbull made an impact while training with the club, earning him a permanent deal until the summer of 2021.
Both Turnbull and Taylor are earmarked to challenge for a place in the proposed reserve team, which had been set for introduction next season.
However, following the financial pressures caused by the coronavirus, Pompey are now weighing up whether to continue with those reserve-team plans.
In March, Pompey’s youth setup swelled their coaching ranks by appointing ex-Pompey player Michael Poke as head of goalkeeping. His responsibilities include coaching the under-18s and a prospective reserve team.
The 34-year-old was previously at Southampton, where he worked with the 9-15 age groups.
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