That's precisely why I'll be buying one: my daughter wants a 3DS, but I said let's wait for the Switch instead. Then we'll get to use it on our main TV (replacing our Wii U, which we rarely use) and have games that work in both settings. Win-win.
If your daughter wants a 3DS to play portable games (with nothing specific in mind) then waiting for a Switch instead of getting a 3DS is probably worthwhile.
If, however, your daughter wants a 3DS for specific titles, you're still better off getting her the 3DS. For example, if all of her friends are currently playing and trading on Pokemon Sun/Moon, getting a Switch will basically have her feeling left out.
In her case it's not for a specific title, so she was excited to learn about the Switch and is waiting for it. For whatever reason I don't see many kids around here playing on 3DS, so peers aren't a factor. (Most gaming with friends happens on PC/Mac Minecraft; I run a private server for them.)
>> delayed gratification is not always a bad thing.
It's not so much about delayed gratification -- when you're talking about a specific game (especially one that is online) on a specific platform, it's more like no gratification at all.
