I wondered the same thing, with yesterday's announcement.

My speculation/conjecture:

(I wish I had posted this yesterday, when I envisioned it) :

I think it will look a lot like a 787. Similar cockpit externally...and internally. Basically, a single-aisle 787.

Gear: methinks it will have long gear like a 757. But, unlike the 757, no four-wheel truck. Too much dead weight. Possibly a two-wheel unit like the Bus or Guppy...or, possibly a three-wheel unit?

Two jumpseats and ability for a rest bunk.

Kicker: I'd bet money it will be a common type-rating with the 787 as a marketing and operating ploy.....and why not? It would make sense for airlines, its been done before, and might be the key to more sales..not only of the 797, but 787.

And I predict it will be the first airplane SWA buys that breaks the 737-only paradigm; ie, they will slowly switch to an all-797 fleet.

And 25 years from now, we will complain about how Boeing is making the 797-1200ER for SWA....

And I would not be surprised if the 737Max10s were converted to 797 orders. Meanwhile, this could be used as leverage on Airbus to get cheap 321NEOs "...or else we'll need to buy more 737s..."