Also keep in mind that Microsoft hasn't actually given OpenAI $13 Billion because much of that is in the form of Azure credits.
So this could end up being the cheapest acquisition for Microsoft: They get a $90 Billion company for peanuts.
[1] https://stratechery.com/2023/openais-misalignment-and-micros...
To be clear, these don't go away. They remain an asset of OpenAI's, and could help them continue their research for a few years.
Which I don't think is impossible at some level (probably less than Microsoft was funding, initially, or with more compromises elsewhere) with the IP they have if they keep some key staff -- some other interested deep-pockets parties that could use the leg up -- but its not going to be a cakewalk in the best of cases.