Berahino scored both of the Baggies's goals in their 2-2 draw against Peterborough United on Saturday in his first start since October 31.
The 22-year-old has fallen out of favour at the Hawthorns after failing to complete a move to Tottenham in the summer, with Pulis accusing him of "wasting three or four months" on Friday.
"It's nice for [Berahino] to get 90 minutes under his belt because that was important today," the coach told reporters.
"He is a good finisher. He's not as sharp, he's not as fit as we'd want him to be, but he's missed half the season and that's going to be a problem for us.
"His goals are so, so important for us and he's shown that again today.
"Everything that happens financially at the football club will be determined by the chairman, but personally I don't think it will be [Berahino's last game]."
Pulis was annoyed at West Brom's failure to see out two leads against their League One opponents but praised Graham Westley's side.
"Firstly you've got to give Peterborough a load of credit," Pulis said. "They've come here and they've worked really hard and they've given it a great go.
"We've had the cup tie twice in our hands and we switched off twice.
"[Sebastien Pocognoli and Boaz Myhill] get caught for the first goal and the second goal is a poor goal for us, an angled ball, we don't defend that on the left-hand side of the pitch that well and the lad takes it with aplomb."
Pulis revealed that a rib injury sustained in training meant goalkeeper Ben Foster was not risked, with Myhill stepping in.
"That was disappointing because we want to keep him playing but obviously the games now come thick and fast," he said.
"Whether he'll be fit for Swansea, we'll have to wait and see."