Williams joined Ipswich on a one-month loan deal on Thursday, having failed to make a Premier League start for the Eagles this season.
The 20-year-old Wales international is lacking in match fitness, according to Pulis, and he says Palace may look to extend his loan with Ipswich.
"When I first came in Jonny had an injury," said the Palace boss. "He looked a bit rusty and in need of games.
"To be fair to him, he's trained a lot better during the last couple of weeks, and we needed to get him out to get some games.
"It had to be a club and a manager that we were happy with and Ipswich fit the criteria on both counts. It's a fantastic football club that has fantastic facilities and great support, and Mick McCarthy is a very good manager who will look after him.
"Johnny needs to play games. Whether we extend his loan we will decide in a month's time. Does he have a future at the club? He has a massive future at this football club."