The England international is out of contract at the end of the season with Tottenham, West Ham and Southampton among the teams believed to be interested in signing the goalkeeper as a free agent in the summer.
Currently serving a suspension following a red card he picked up against Cardiff, Johnstone missed Albion’s FA Cup defeat against Brighton and will also sit out the upcoming Championship games against QPR and Peterborough.
Ismael, though, thinks the break will do the keeper good.
And he is hoping when he returns, Johnstone will play a key role as the Baggies battle to win promotion.
“At the minute I am pretty sure that he will stay,” Ismael said when asked if he expects Johnstone to still be an Albion player next month.
“But you never know what can happen in football.
“If a keeper gets a big injury and a club needs to replace him you never know what the situation could be.
“But at the moment it’s not the plan for Sam to leave us. We want to have all the players.
“Now Sam needs a break and he has his break to reflect, come back stronger and help us in the season.”
Having been part of the England squad that reached the final of the European Championship in the summer, Johnstone didn’t get the chance to switching off during the close season.
“It is a good time for Sam to have a break because if you look back at the summer he never had a break,” Ismael continued.
“He played through with us and the national team so now it’s time for him to reflect for a bit and at the same time it’s a big chance for David (Button) to step up because he deserves it.
“Now is the time for Sam to switch off.
“If you see all the training sessions and matches he had in the last six months, there were a lot of signs that Sam needed time to breathe, to refresh and to reset and come back with big motivation and another big build-up in his preparation so it could be a good situation for us.
“We have another very good keeper with David to play and it allows Sam to have a break, recharge and find himself back with his strength.”