Even without a recon mission, I'll share some initial best guesses as to future-Isaias's peak intensity. This is not necessarily intensity at landfall.
HIgh end Tropical Storm, however, I could be wrong, follow the official advsiores. If it makes it to the forecast windspeed it would take a Milton like fall apart (weakening) to drop down. Increases tornado risk for well east of Landfall if that occurs though.