The title seems to promise that the characters will end up together, but for long stretches it's hard to see exactly how they can ever get there.
The title doesn't really promise that they'll get together. But it does seem to promise that Touko will overcome her identity problem. "Eventually, [no subject] will become you" & "Bloom into you". I posted one interpretation earlier that "you" means "oneself" due to the inherent lack of subject in both the official titles given by Nakatani herself. You can see a more universal coming-of-age theme coming through with this interpretation, so Touko might be able to find herself eventually.
I've read another interpretation where someone points out the use of "kimi" is how Touko addresses Yuu, so they suggest that the title refers to Touko eventually becoming more like Yuu, who is essentially gentle, kind, patient, has lots of self-control, & above all, mature. I think it's an interesting interpretation since Touko's characterization has been like that of a child. Gonna go on another stupid ramble here, but I absolutely love the tunnel scene in this chap. Aside from the fact that it looks gorgeous, I also love how the sequence plays out with Touko being lost for a moment there (like a kid) then Yuu grabbed her hand & guided her through the beautiful tunnel. But yeah, the latter interpretation zones into Touko's coming of age specifically.
Touko overcoming her problem doesn't necessarily promise that they'll get together though since some ppl, & even Yuu herself in this chap, have been bringing up the question of whether Touko's feelings for Yuu are genuine love or just fleeting infatuation. Personally, I still stand on the view that Touko's feelings have grown to be more genuine over the course of the story, it's just still misguided atm & her overcoming her problem will be the necessary step for her to come to embrace these feelings. But I agree that series can go either way at this point.