There's no reason why they couldn't give Lorraine a GMB style set in TC2 to be honest (once normality resumes, at least) - gives the opportunity to expand the GMB brand, and allows This Morning to set up and prep.
Is Lorraine still rating higher than GMB? I’ve not heard how it’s performing in its slightly later slot.
If it’s still been outperforming GMB, as I suspect it has, I doubt they’d want to bring it in line with a lower rated brand. Also the two programmes have a very different feel. Lorraine’s show is a lot more soft and gentle, and in normal times, I don’t think it’d suit GMB’s more brash style.