Who knows how this will play out, but user behavior is always somewhat sticky and OpenAI now has 400M+ weekly active users. Currently, I'm not sure there is much of a moat, as many would jump if, say, Google released a model that is 10x better. However, there are myriad ways that OpenAI could slowly try to make their userbase even stickier:
1. OpenAI is apparently in the process of building a social network.
2. OpenAI is apparently working with Jonny Ive on some sort of hardware.
3. OpenAI is increasingly working on "memory" as a LLM feature. Users may be less likely to switch as an LLM increasingly feels like a person that knows you, understands you, has a history with you, etc.
4. Google and MSFT are leveraging their existing strengths. Perhaps you will stick with Gemini given deep integration with Android, Google Drive, Sheets, Docs, etc.
5. LLMs, as depressing as this sounds, will increasingly be used for romantic/friend purposes. These users may not want to switch, as it would be like breaking up and finding a new partner.
6. Your chat history, if it can't be easily exported/imported, may be a sticky feature, especially if it can be improved (e.g. easily search, cross-reference, chats, like a supercharged interconnecting note app with brains).
I could list 100 more of these. Perhaps none of the above will happen, but again, they have 400M weekly users and they will find ways to keep them. It's a lot easier to keep users that have a habit of showing up, then getting them in the first place. There's a reason that Google is treating this like an emergency; they are at serious risk of having their search cash cow permanently disrupted if they don't act fast to win.