It is possible, but hardly believable.
'Obi-Wan Kenobi' is one of Disney's recent bold takes on the Star Wars universe, with creators proceeding to deliver their own view of the story that sometimes does not quite fall in line with what fans expect. Preemptively anxious about the possibility of the TV series retconning 'Star Wars' movies, fans have blasted Kenobi when they saw Reva spiking the Grand Inquisitor with her lightsaber.
The scene looked pretty much like Reva killing him, even though he was clearly not supposed to die during the events of 'Obi-Wan Kenobi', given that his death in the show would be a huge breach of the canon.
However, it might be too soon to tick out the Grand Inquisitor from 'Obi-Wan Kenobi'. The series has never shown him actually dead, only having him falling to his side after being stabbed by Reva. This could mean a lot of things, and fans remain 99% confident that the Grand Inquisitor will most definitely return.
This is not only because the Grand Inquisitor's fate is decided in 'Rebels', but also due to many other factors. In fact, fans remain worried over him for many different reasons. Many have noticed that Reva has shown quite an attitude over the course of the first episodes, and given that the Grand Inquisitor's position as second to Vader implies an ability to foresee events and prevent rebels, people believe that the Grand Inquisitor simply could not be that stupid to allow Reva to kill him.
"Am i the only one who thinks the grand inquisitor's death completely disrespected his capabilities? He was an absolute force of hell in rebels. And he gets such a disgraceful death with no warning? Also – I thought he died in rebels?" – @_burntlime_.
According to fans, the Grand Inquisitor is most likely to re-emerge at some point and expose Reva's betrayal, effectively becoming someone who could possibly kill her at the end of the show.
But some people are ready for the worst scenario of the Grand Inquisitor really dying – something they believe would be a huge storytelling mistake in 'Obi-Wan Kenobi'.
"So, they really did retcon the Grand Inquisitor's death. Such horrible story-telling in part 3 of #ObiWan . Vader can't go AROUND a fire? More Leia shenanigans and Obi-Wan just goes along with it? And Reva somehow gets ahead of Leia? This thing is a train wreck," – @ronkopop.
The backlash over the plausible death of the Grand Inquisitor was in fact so huge that the show's writer, Joby Harold, had to weigh in and borderline spoil things, saying that "we would never break canon" and "canon is everything" when commenting on this "death".
If that is not an explicit hint that the Grand Inquisitor is perfectly fine, then what is? Some fans were even disappointed with the mere fact that Harold had to clarify that only to calm the enraged fans down.
However, should the death of the Grand Inquisitor somehow turn out to be real, it would definitely retcon the 'Star Wars' canon – something that 'Obi-Wan Kenobi' has already faced backlash for after the purported plot leaks claimed that Kenobi will fail to protect Luke, and he will survive due to Reva's sudden mercy exclusively.
It is unknown whether the leaks are true, but clearly fans will react bitterly to any kind of retconning the already established events in the 'Star Wars'. 'Obi-Wan Kenobi' will conclude in late June, with two remaining episodes to be aired on Disney Plus.