It depends
Koby needed Prince Grus and Garp's massive help to barely do a thing to Pizarro, who is just getting used to his powers and will certainly get stronger before he fights a Strawhat.
On paper, if he is ever going to be able to fight EQUALLY with Luffy, then yeah, he should be stronger than any Strawhat except Luffy.
Otherwise he will at best be comparable to Zoro or to Sanji, these two might be around Sabo's level EoS i believe