How a character dies isn't as important as how other people react to his death. This creates some real narrative opportunities, for instance starting a film with someone saying "T'Challa is dead!", and then exploring not just how and why, but the consequences.
Maybe, but it also eliminates an iconic and very well received character whose stories they had only begun to tell. It will also mean that Black Panther is dead in the movies, but alive and well in the comics, which creates issues when adopting comic storylines into future movies.
This last point is the weakest. There are a huge number of differences between the comics and movies -- keeping continuity between them has never been a major point, nor should it be. I think the comics have been useful to mine for the best storylines -- I thought the Killmonger storyline was a great example of this. But Black Panther in the comics hasn't been solely about the character of T'Challa. It is a title that has passed from person to person. There are a lot of cases of characters other than T'Challa who have been Black Panther in the comics - including Shuri as well as Kasper Cole and even Killmonger.
The only two significant recastings in the MCU have been Hulk and War Machine. The Hulk was largely by ignoring the original movie which effectively isn't a part of the continuity, and War Machine was a minor side character prior to replacement.
I think it will work better if the actor playing the new Black Panther can fully own their role -- bringing their interpretation to the role, rather than being tied to how Chadwick Boseman interpreted T'Challa.
Also, I like the idea of Shuri as Black Panther because thus far in the MCU, T'Challa hasn't been portrayed to be a scientist -- and we've been lacking superhero scientists in the MCU. In the comics, Black Panther is a brilliant scientist and engineer who is a peer to Reed Richards and Tony Stark. In the MCU, Reed Richards has been missing; and Ant-Man is Scott Lang rather than Hank Pym (Pym hasn't interacted yet with the rest of the Avengers). There is Bruce Banner as a scientist and Tony Stark as an engineer, but they could use some company.