With the Lanterns finale just a few hours away, fans are flooding the internet with theories about Hal Jordan's death. Reddit is filled with theories about what could've been the events that led to Hal Jordan's death. One such theory suggests that Hal Jordan might have communicated to John Stewart what the latter should do after the Green Lantern legend's murder.
The HBO series has mostly kept a tight lid on the Hal Jordan murder mystery. Therefore, the iconic Green Lantern legend's murder has been the most discussed aspect of the HBO series ever since the DCU series premiered two months ago. The first episode ended with a flash-forward to 2026, which revealed that Hal Jordan is dead. Since then, the HBO series did not return to this mystery until Lanterns Episode 6.
Thus, one fan has suggested Hal knew that he was on borrowed time when Hal and John met in the first act of the sixth episode.
Explaining this Hal Jordan Lanterns fan theory:

One Reddit user, u/Purple_triangle_guy, put forth a long theory analyzing Hal Jordan and John Stewart's interaction in the Rushville cafe in the first act of the sixth episode, which returns to 2026. If this user is to be believed, Hal was instructing John Stewart what to do in case he died. We also believed that John might have realized that Hal basically instructed him during their last interaction after learning about Jordan's murder.
Thus, the first thing John did before burying Hal Jordan was to call Guy Gardner using the Green Lantern signal, which was influenced by the Bat-Signal. Hal may have even instructed John to summon the backup consciousness by joking that someone should tell Guy that the Green Lantern constructs need not be the shade of green that we saw Guy's constructs being in last year's Superman.
Thus, John summoned the consciousness using Hal's decommissioned ring, which he got by digging up Jordan's grave in the closing minutes of Lanterns Episode 6. We learn in the seventh episode that John wanted the backup consciousness to open the voice-activated safe, which can be opened only by Hal. Since the consciousness retains Hal Jordan's appearance, the safe opened as soon as this version used its voice.
This is where we believe that there is more to this fan theory.
Hal may have wanted John Stewart to visit the alien planet:

The fourth episode of Lanterns established the fact that Hal looked up to Sinestro during their time in the Green Lantern Corps. Thus, it seems that the DCU might be giving us a Sinestro who might be right about the Guardians.
As of now, we have only seen one Guardian, Lianna, and even she has been acting suspicious since the beginning. The seventh episode revealed that Hal had a portal to a destroyed alien planet, a gun, and a poncho inside the voice-activated safe.
John and the backup consciousness visited the destroyed alien planet. John told the consciousness in Hal's ring that the destroyed alien planet is Antaan's home world. A Manhunter doused this planet with the fear gas, which made the residents tear themselves apart. John noticed a mysterious factory on an island in the middle of the lake. John was rowing the boat towards the factory when it started to rain.
As soon as John was exposed to the rainwater, he began to hallucinate his fears, including a younger version of himself. Hal's consciousness snapped John out, and the latter deduced that the fear gas was still in the rainwater. Thus, the next time we saw John row the boat, he was wearing the poncho we saw in Hal's safe.
Sometime later, the two reached the mysterious factory, where the two encountered Sinestro, ending the seventh Lanterns episode. Therefore, this week's finale will resume right where last week's episode left off. But the inclusion of a poncho suggests that Hal regularly visited his former mentor on that planet. If Hal visited his old mentor, we believe that he was teaming up to investigate the Guardians.
We think that he might have even considered joining his old mentor's Yellow Lantern Corps. But given that Hal is dead in the series, John Stewart could join the Yellow Lanterns in the HBO series. This may feel surprising, but there is precedent for John being a Yellow Lantern, as he joined this Lantern Corps in the Green Lantern: Earth One comic. However, John is a hero even as a Yellow Lantern in the Earth One comic.
John becoming a Yellow Lantern could also reveal why the Lanterns' marketing material used the tagline, “Only one can wear the ring”. John joining the Yellow Lantern Corps would give the DCU prime Earth two Lantern Corps members, but both of them use different rings powered by different emotions.
Lanterns Episode 8 airs on HBO tonight at 09:00 PM ET/06:00 PM PT.