No. She will steal Noel away from Serah. Noerah will cease...it will be Noemina.
That coupling name made me realize that Lumina is the Namine to Serah's Kairi. Namine was a Kairi clone(albeit with blonde hair) that was designed to both urge Sora through Castle Oblivion and distract him from his real goals, just like Lumina helps Lightning and gets in her way too.