As the previous answer well states, it appears to be inconsequential to The Last Jedi.
However, it will greatly impact Episode IX
What’s perhaps all the more maddening is the reveal that Episode IX
would have put Fisher’s Leia front and center, in the same way that
Harrison Ford‘s Han Solo was at the crux of The Force Awakens, and
Mark Hamill‘s Luke is at the heart of The Last Jedi. Kathleen Kennedy
confirms, “The minute she finished, she grabbed me and said, ‘I’d
better be at the forefront of IX!’ […] She thought IX would be her
movie. And it would have been.”
http://collider.com/star-wars-episode-9-carrie-fisher-role/#rian-johnso
As the world still grapples with the fact that Carrie Fisher is gone,
the galaxy far, far away is coming to terms with the loss of its own
princess general.
Lucasfilm president Kathleen Kennedy tells EW the story team and
filmmakers have come up with a plan for how to handle Fisher’s absence
in 2019’s planned Star Wars: Episode IX.
The actress won’t be recreated digitally, but unfortunately, that also
means Leia Organa won’t be a part of the story.
“Obviously, with Carrie having passed away, it shook everybody,”
Kennedy says. As they tried to figure out what this meant for Leia’s
continuing story, the only option was to leave their original ideas
behind. “We pretty much started over,” Kennedy adds.
http://ew.com/movies/2017/04/14/kathleen-kennedy-episode-ix-carrie-fisher-death/
In addition it should be noted that Collin Trevorrow is no longer
directing/writing episode IX. Some reports suggest that he was slow on
drafts, but given Carrie Fisher's death, one might speculate the
rewrights were too taxing being a relatively newer film-maker. JJ
Abrams has now taken back the reins on both counts. Also early on it
was stated that Carrie Fisher would not be CGI-ed into the films, but
this was also when they stated would put things on pause for a while
(as far as the public is concerned)--recently Billie Lourd did become
the benificary of Carrie Fisher's estate and there might be room to
argue that Disney/Lucasfilm was waiting for that and that Carrie's
presense in the film could change in some way, considering the
following tadbit from Trevorrow before he was fired:
"She was a major character, that's not a secret," Trevorrow, who
didn't get the chance to meet Fisher before her death, said in a
recent interview with Cinemablend while promoting his upcoming
film The Book of Henry. "It was extremely sad for all of us, mostly
just because she was so loved by the Star Wars family and everyone
that worked with her. I feel like our options are limited mostly by
ourselves, in that there [are] only certain things that we are willing
to do. But I can guarantee it will be handled with love and respect,
and all the soul that Carrie Fisher deserves."
Lucasfilm head Kathleen Kennedy revealed in a recent interview
with Vanity Fair that the company has no plans to recreate Leia
digitally for the film, and will instead find a way to honor the
character without Fisher present. Still, she said, Fisher's loss was
deeply felt. "Because Harrison [Ford] was front and center on VII, and
Mark is front and center on VIII, [Fisher] thought IX would be her
movie," Kennedy said. "And it would have been."
Read More:
http://www.looper.com/68990/trevorrow-star-wars-9-carrie-fisher/?utm_campaign=clip
UPDATE: The Force Awakens unused footage will now be used in Episode IX and Carrie Fisher (Leia) will be included in the film:
“As we, her family, as well as her extended family of fans around the
world so believe, Carrie’s ‘Princess Leia is forever entrenched in the
franchise and her indelible presence is fundamental to the film,” Todd
Fisher said. “J.J. Abrams understood Carrie’s iconic role, and he
has masterfully re-crafted this final entry to include this unused
and very last footage of Carrie ever taken, without resorting to CGI
or animatronics. Our family and her fans will look forward with great
anticipation for this one! Her force will forever be with us!”
Cast Press Release for Episode IX also includes Carrie Fisher's name:
Star Wars: Episode IX will begin filming at London’s Pinewood Studios
on August 1, 2018. J.J. Abrams returns to direct the final installment
of the Skywalker saga. Abrams co-wrote the screenplay with Chris
Terrio.
Returning cast members include Daisy Ridley, Adam Driver, John Boyega,
Oscar Isaac, Lupita Nyong’o, Domhnall Gleeson, Kelly Marie Tran,
Joonas Suotamo, and Billie Lourd. Joining the cast of Episode IX are
Naomi Ackie, Richard E. Grant, and Keri Russell, who will be joined by
veteran Star Wars actors Mark Hamill, Anthony Daniels, and Billy Dee
Williams, who will reprise his role as Lando Calrissian.
The role of Leia Organa will once again be played by Carrie Fisher,
using previously unreleased footage shot for Star Wars: The Force
Awakens. “We desperately loved Carrie Fisher,” says Abrams. “Finding a
truly satisfying conclusion to the Skywalker saga without her eluded
us. We were never going to recast, or use a CG character. With the
support and blessing from her daughter, Billie, we have found a way to
honor Carrie’s legacy and role as Leia in Episode IX by using unseen
footage we shot together in Episode VII.”
Composer John Williams, who has scored every chapter in the Star Wars
saga since 1977’s A New Hope, will return to a galaxy far, far away
with Episode IX.
Star Wars: Episode IX will be produced by Kathleen Kennedy, J.J.
Abrams, and Michelle Rejwan, and executive produced by Callum Greene
and Jason McGatlin. The crew includes Dan Mindel (Director of
Photography), Rick Carter and Kevin Jenkins (Co-Production Designers),
Michael Kaplan (Costume Designer), Neal Scanlan (Creature and Droid
FX), Maryann Brandon and Stefan Grube (Editors), Roger Guyett (VFX
Supervisor), Tommy Gormley (1st AD), and Victoria Mahoney (2nd Unit
Director).
Release is scheduled for December 2019.