Clarke receiving the Nightblood injection does not mean she’s going to take the chip and become the next commander, remember at this point Clarke doesn’t even know where the chip is. I also think the Nightblood injection will be good for Clarke personally and for Bellarke:
Why this will be good for Clarke and why she won’t be taking the chip:
Clarke doesn’t need the chip to become a leader, she already is-think back to Ep 1 of this Season when Kane told Abby: “The youth shall inherit the earth.” Clarke and Bellamy are taking over leadership of the Arkadians from Kane and Abby and this is just another step forward on that journey. To have Clarke take the chip would be a step back on her leadership journey.
Clarke needs to become a leader in her own right, not one who just follows the advice she got from L/xa. so Clarke injecting herself with Nightblood could possibly be one of the first real steps we see Clarke make to becoming her own kind of leader, not just one who parrots the advice of the leaders shes known.
To extrapolate on this idea that Clarke is going to finally begin to come into her own. One of L/xa’s key pieces of advice was: “You have to be willing to send others to fight and die for you” (paraphrasing). Well, Clarke’s already tried this method twice now: the first time with the Grounder guy and then in even considering Emori. In choosing to use the Nightblood on herself, she shows hat she is willing to sacrifice herself (something we haven’t seen Clarke do before) for her people, which…is extremely reminiscent of one Bellamy Blake.
I also suspect that the Nightblood will wind up protecting Clarke from the ill effects of radiation at some point in the future.
Why this will be good for Bellarke:
Back in November (around the time they were filming 409 and 410), Bob gave an interview where he said that Abby and Bellamy are always united in wanting Clarke’s safety and something we would see in the later episodes of the Season.
Clarke will obviously be a radiation test subject now, they have no choice it would be a waste of perfectly good Nightblood if they didn’t and so, like Luna, she too will suffer temporarily from radiation poisoning. I believe Bellamy will be informed/figure out that Clarke is suffering from radiation poisoning and come to her.
I think this will bring the foreshadowing in 406 (Bellamy: “Clarke, if we don’t see each other again…”, Clarke: “We will.”) full circle and open the door for emotional (possibly romantic) confessions.