Mario Gotze is heading to rivals Bayern Munich, Dortmund's Champions League conquerors at Wembley, while Polish striker Robert Lewandowski is also expected to leave.
But Hummels is confident manager Jurgen Klopp will unearth fresh talent to continue their upturn.
"Of course it is going to be hard if we have two of our best players going but others can come in and take their place," said Hummels.
"We don't buy stars, we don't buy big players, we make them in to stars and that' s the way I really like it.
"It's going to be really hard but we know we will get some new players and I am really looking forward to that.
"We have showed how well we can play. We want to prove it further in the coming years, and I hope we will achieve that and make it to the final again."
Dortmund succumbed to Arjen Robben's 89th-minute goal after a pulsating final and Hummels admitted they paid the price for focusing on the likelihood of extra time.
"We started thinking about extra time," he added. "I don't know how we let Bayern play so many long balls, and from one of them they managed to score the second goal."
His fellow centre-back Neven Subotic, who had been an outstanding leader in the rearguard action as Bayern searched for the late winner, claimed there was more than a touch of fortune about Robben's goal.
"It was kind of depressing how they scored that second goal," he said. "I'm not sure that [Franck] Ribery wanted to backheel it to Robben, but that's how football is.
"You've got to take it for what it is and learn from it. We are a young team, that's for sure, and we're going to take this as a lesson and move forward.
"This would have been the top of the mountain. But we got so far, and it was a great journey up until now.
"It was anything but a bad performance today, so we can't really say that we didn't try and didn't run.
"We might have set a new running record; that's what it felt like today.
"We really gave it our all, but, in the end, in football sometimes luck decides the match and that's just how it is."
Marco Reus, Dortmund's German international forward, admitted it had been a sickening blow to lose so late.
"I felt so empty, we were desperate to win the trophy, so to concede a goal in the last minute like that was hard to take," he said.
"I think everyone could see that Bayern weren't unbeatable. They showed us the respect we deserved, but we didn't win the cup and that's all that counts."