Yes, but you would be seeing ALL posts from everywhere your instance knows about.
I kind of like the idea of being on lemmy.world, filtering to say aussie.zone and getting it to show me local.
Or being able to simply get a list of every community on another instance.
These are cool ideas.
The first 90% of the task takes 90% of the time.
The last 10% of the task takes the other 90% of the time.
Threads will mainstream threads.
Any good content here will be available to the Threads users, who will be oblivious to where it is coming from.
Eventually, Meta will take steps to break compatability, and lots of the most prolific contributors from here will move to Threads exclusively (for a host of valid reasons).
When it is no longer in Meta interest to federate, they will stop.
The fediverse will continue, but it will be weakened by it’s temporary reliance on Threads (who could afford to host large images/videos/etc, have lower latency, etc etc).
The US (which is where I assume you are), has the second largest one in the world in current operation:
https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Station
Short answer, it scales fine.
Now you need to find someone to pay for it.