Virgil van Dijk claims he knows nothing of interest from English clubs and is keen to prove himself in the Champions League with Celtic.
QPR loanee Tom Carroll wants to "make it at Tottenham" but is prepared to consider all of his options at the end of the season.
Seaborne has won three and drawn one of the four matches he has played in since making the temporary move to The Valley.
The 25-year-old was forced to sit out the final match of his original loan spell, last Saturday's 2-2 draw against Brighton.
But Seaborne will get the chance to extend his unbeaten run in the Charlton team after a fresh deal was struck.