I know Apple’s developing their own LLM which will hopefully be used in Siri. There’s no guarantee, but I can’t think it would be too hard to add Bard into Google Assistant. Cortana on the other hand was canceled by Microsoft and is being replaced by Bing chat. I believe Amazon is also stopping the Alexa development
I use my iPhone extensively and it consistently lasts me all day. The iPhone 11 Pro came with a 20w charger in the box (although admittedly they removed the power adapter from the 12)