The underlying MBA principle is that companies strongly prefer to focus on their "core competencies." This makes sense because the distraction to a business could be much costlier than the extra money spent in outsourcing non-core functions.

This is basically also why the cloud business was thriving even when on-prem is much cheaper in monetary terms, and why the trend will probably extend to cloud AI providers even when open weight models get better. (As an example, Linux is free, but MSFT makes a ton of money off it by renting out the hardware it runs on.)

That said, there will likely also be a very large volume of internal SaaS-y apps that enterprises will vibe-code simply because nothing on the market meets their needs and/or price point.

Another possibility is enterprises "remixing" existing SaaS apps for custom functionality by adding their own vibecoded layers on top of the SaaS endpoints. Either invoking official APIs where available, or by less official means like using custom browser extensions. Now that could lead to some interesting dynamics...