the more important question is how are we gonna preserve the Virtual Boy games

It would depend on the game. Games that use the 2nd screen for a map or menus would be pretty easy to port over, but ones that has a unique use would be harder to do, if it can be done at all. I figure only some games could be ported over to the Switch, but may only do a few DS titles, as it mat take up a lot of work to port over a lot of DS/3DS games.

"Can" is miles apart of an "ideal way to play".

And that's what I'm talking about, it just works, but I'd hate to play a game in that way. To be honest, even locking the DS/3DS virtual console to docked mode and having the small screens displayed on the TV seems like a better idea.

I think it mixed would work best

Side by side if the game can work without being verticle, Wii U styled if the bottom screen is not important, and vertical if the touch screen is needed or the game needs to be vertical.

If the Switch is vertical, you can still detach the joycons and play with the screen propped up

They will launch a dual screen mini switch.
The upper part would be a mini(but extensible) switch, with mini joycon. The lower part will be like a 3ds lower screen, without the controllers. You can take the joycon off the upper part and put in the lower part, and the device would look like a 3ds.
Of course, you can hide the lower part behind the upper by a trail. Also, the lower part will have ds and 3ds slots, mic and the camera.

Other option is to get a switch, shrink, put the joycon trails also in the upper and lower sides of switch, take the joycon off, turn the switch 90 degrees, put the joycon on the new trails, and it would look like a 2ds. A single screen in vertical simulating 2 screens...

Anyway, I think the way to incorporate is in a new revision, more handheld orientated.

vertical switch?
Also Nintendo can add Stick C in each Joycon (it is a good idea)

Why would they do that? It would just be another Wii U scenario where nobody actually uses the dual screen because a lot of the userbase wouldn't have one ... 

If anything it would be like the SP where there isn't a dual screen.

Oh ok, sorry I was just curious about what led you to that conclusion

Although a few other people already said that

With option to use joycon and disable onscreen buttons.

Piracy.