As far as I've read so far Apple is adding RCS support to the Messages app, aka alongside SMS & MMS: https://www.theverge.com/2023/11/16/23964171/apple-iphone-rc...
It's not clear if iMessage will interoperate via RCS, which is what would make blue/green bubbles less relevant. My assumption would be no as they'd cede moat, and there isn't much of a network effect for them to gain from.