There is nothing preventing a possible ARM Mac to feature 16+ GB of RAM
There isn't anything preventing a 16GB iPad, but there isn't one, and probably not for a while. Related to this particular thread, which is 'lack of RAM is a hardware issue'.
Well, the Mac isn't going away any time soon. Almost certainly not for a decade.
No, they will be around for a while, thankfully, and unlike what some say, Xcode won't be the killer app iPad app that 'dooms' the Mac.
Well, where there's demand, there's a way.
As for tools executed from the command line: yes, that, too, can be done. For example,
https://github.com/ColdGrub1384/LibTerm has a sandboxed Unix with Python built in.
All these tools are good, but they still won't work: They are isolated via the sandboxing, and my workflow demands interaction between IDE / command line / and other tools - and there is't an iOS app that could satisfy this.
All this is trying to shoehorn development into an iPad, which really isn't practical for me today, or for the foreseeable future. iPads are good for some things, but not for others. A Mac is a great development platform, the iPad not so much. I'm not going to change my workflow to one that is less than what I'm do today. I want to improve my workflow not regress.
Still, after all this, RAM is an issue. 6GB? Forget it.
Use the best tool for the task as required, which is why I'm using a Mac, not an iPad or anything else.