While it definitely appeared as if Hela died at the end of Thor: Ragnarok when Surtur destroyed Asgard, common sense says that the Goddess of Death is currently ruling over Hel just like her comic book counterpart. During a recent interview, actress Cate Blanchett acknowledged that while the villain "looks pretty dead" after what happened, there's a possibility she could make a return to the MCU.
"There’s always a way back, but I’m sure there’s always a way forward, who knows? Sure. I never say no to anything." As for a possible team up with Thanos, Blanchett said that such a pairing has potential but notes that it would be "not nice." Hela is the closest thing the MCU has to Death, so many fans were actually surprised when she didn't align herself with him in Avengers: Infinity War back in April.
As you can see in the video below, Blanchett even thinks there's a chance Hela could be redeemed and turn good and seeing as her comic book counterpart has helped the God of Thunder out over the years, that's definitely one possibility. Then again, seeing as Marvel Studios rarely brings back its bad guys, it's hard to say what could happen. However, she may just factor into Avengers 4...time will tell!