This is obviously just me pulling things out of my ass (about things that are not even confirmed and people I don't actually know) but I can see "Kalafina" being important/precious to Keiko (both as the unit itself and the 10 years of her life) and her wanting to protect what it was to her. It's not sneaky (unless she uses it for her own gain) - (edit:) it's smart. But I'm talking out of my ass...
I see it like that. I can even see Wakana and Hikaru agreeing. Kalafina is the time they spent together, their effort, their success... I'm sure Keiko wishes the best for the other two, but just not under that special, meaningful name. Kalafina is also a word "crafted" by Kajiura just for them and their music. Without Kajiura and Keiko, it'd be weird to keep the name.
What makes me sad is thinking how much the girls must have suffered all this time. The trademark request was from last year, so the probably did their Live Anni concert knowing it would be the last, yet they tried to perform the songs we wanted and did their best on that huuuuge setlist!
And Keiko writing that precious message to Hikaru and Wakana on the radio program
Even with everything going on, the girls keep being so sweet, I'm sure they love Kalafina as much as we do.
This notice really made a huge impact on me because Kalafina means a lot to me. I spent all my day wanting to cry, they're like my children, I saw them growing up and evolving. But at the end of the day, I'm grateful. No matter what happens from now on, they did amazing things. They helped me a lot. They made me happy. Those things will never dissappear. I'm support the girls wherever they go, and I'm sure they'll keep making amazing things! Ofc it'll be hard for Wakana and Hikaru to work by themselves (specially with Hikaru's voice problems) but they'll find a way. And Keiko has an unique, fascinating voice, an attractive personality and she's so damn pretty so I'm sure she'll be sucessful wherever she goes.
I just want to thank them for everything. I wish I could fly to Japan and tell them "arigato". Thank you, thank you a million times, Kalafina.