Simpson reiterated his determination to hold onto the frontman, who has two years remaining on his current contract at the club.
"We are in the fortunate position at this football club where financially we don't have to sell," he told the club's official website.
"There have been a number of rumours circulating about Grant leaving the club but I am still planning for Grant Holt to be wearing our number 16 shirt next season."
Simpson also confirmed Holt's recovery from ankle surgery is progressing well.
"He is very close to starting to jog, the plan is that he will be going to Lilleshall for some intensive rehab and will hopefully join the rest of the squad in the middle of July," the Shrewsbury manager added.