WWGRM do with this rust?

My car collective has a 2008 Scion xD. It's actually a surprisingly fun car to drive. I'm shocked how much I like it. But it is pretty rusty. 
 

Im new to rust, having lived mostly in the West. I'm wondering what, if anything should be done about it. Would evaporust or some other product be a good idea? 
 

we had a shop check it out and they said it's not in the "frame." Yet.

Id love to hear your thoughts.

There isn't any spray on wondergoop that will replace missing metal

If it isn't structural and passes inspection, leave it alone and drive it until you can't.  

Sounds good! Thanks

A friend of mine had a PT Cruiser that had some similar rust along the rockers.  She just needed the PT to limp through until her Bronco finally arrived (which turned out to be two years) so I sort of trimmed around the edges to make it a little bit less likely to snag things, especially pants or dresses as one would enter or exit the vehicle, and then sprayed on some Eastwood Inner Frame Rail coating all up and down the channel.  It certainly won't fix it, but if you can slow it down a bit you can get some more life out of it.  On the PT, the rust remained in stasis for two years before the Bronco finally came in.  I'd check it out every month or so just to make sure and what was left stayed solid.

If it's not at the frame yet you can cut out the rust and paint the area in an anti-rust paint of roughly the same color. The shop might be willing to do that for a decent price.

Drive it into the grave.

Side note...

I know you put it in quotes, but a Scion doesn't have a frame. It's unibody. (As you know). 
 

Rockers are generally considered part of the structure of the car in a unibody. 
 

I agree with others who have said drive the wheels off it (especially if you enjoy it!), but make sure the shop you asked is knowledgeable in unibodies. Their response is a (mild) red flag. There is quite a bit of metal missing  there. 

Yeah looking closely at it, even if it has a replaceable outer rocker (which is uncommon) there is some rust on the unibody section behind it which is the frame. A typical unibody looks like this, usually including the rear quarter panels and complete rocker/sill area:

On that car, the rockers are probably part of the 'uniside' which is the entire door frame, rocker, pillars and probably the quarter panel. A very expensive part you must then cut out what you need and toss the rest.

Run it till it isn't safe. Not a valuable enough car to do anything else with.

With that much rust in the rockers, I'd want to take a really close look at the rear suspension mounting points.

edit: at least that was a trouble spot on the earlier Scion Xa/b. Just realized this one was a later version of the Scion box-mobile which I don't know if different

@wae, that's an interesting idea. Thank you. I figure spraying something like on that might at least slow down the rust. I know that metal isn't growing back, ha. But maybe that would at least slow it down.

@Sv Rex, it was a shop that specializes in Subarus, so I figured they knew what they were talking about given those cars are unibody too (as far as I know). To be clear, my neighbour talked to the shop, so the word "frame" but was a poor translation of what the shop said. 

@BlueinGreen, I have checked them out, they look fine. Thanks for the tip tho.

@GameboyRMH, thanks, that's good to know. I think it's definitely eating into the unibody at this point given that pic.

How does a person know when it's no longer safe to drive? Does the chassis start to flex to an alarming degree, or what happens?

In reply to CyberEric :

Doors pop open when entering driveways, seatbelts can be removed without tools, that sort of thing.

You could do a judicious run of cleaning, rust neutralizer, and POR 15 with an overspray of topcoat in a can as a way to slow it down possibly. Sucks tho.