Actually I'm pretty sure that the changes ~present Naho&the gang have made to save Kakeru created a new time line, a parallel universe, so the timeline in which Kakeru dies and Suwa&Naho have a kid still exists. I think that was established at some point in the manga. Still sad for ~present Suwa though obviously.
Ooh, if there is indeed a parallel universe, then that would be a win-win outcome for both ships! :D My getting happy for Kakeru getting a chance to live is always conflicted with Suwa’s sadness and I don’t know how to deal with that.
There also’s my other *tragic* theory that no matter what, Kakeru will die but not in the same way (don’t mind me, just preparing myself for the worst here) and future!Naho is just trying to put closure in her past with Kakeru so she can fully concentrate on future!Suwa (just like in HnR). But since this manga is heavily focused on friendship rather than in romance, I’d still be happier if Kakeru lives even if he doesn’t end up with Naho.
(Btw, I’m reading this manga called Henyoku no Labyrinth/Katayoku no Labyrinth in mangalator where the heroine also dies in the future and her potential OTP is trying to save her life by doing time leaps. Not as great as Orange but it has some nice suspense. You can read it here.)