My guess is that SaaS will be around, but it's going to look really different.
Say there's a company that sells you a subscription to an issue tracker. At first, it looks just like any other web-based issue tracker. But, although you won't realize it at first, it's hosted on a Linux VM with a development environment on it. Each customer's app gets built from source.
Then, when you want something changed, you send a message to support. And they just bounce it to a coding agent that edits the source code and rebuilds it.
The sort of customization that enterprises used to pay big bucks for is going to get dramatically cheaper.
(There are technical issues making this safe, but I think they'll be solved.)
Now where's my customized toaster?
Maybe I'm a luddite, but this seems far fetched, to me. I just don't see a path for LLMs to make all kinds of changes to a codebase from non-technical people, correctly. Yes, LLMs can do amazing things, but they still don't have a mental model of what a thing is doing and make all sorts of weird decisions that are not what you want.
I believe LLMs are going to make the bar for a SaaS you would pay for, as a company, higher.