So, I did a bit of digging and calculating for when the DS Lite and 3DS XL launched in Japan and how they affected DS and 3DS sales respectively before and after their launch.

DS Lite - Launched March 2, 2006:
Before: 43,765
After: 124,286 - 184% increase

3DS XL - Launched July 28, 2012
Before: 43,291
After: 239,273 - 453% increase

This is how the Switch Lite would affect sales next week if it has one of those two percentage increases:
Before: 51,619
After (184%) 146,590
After (453%) 285,303

We should expect the Switch Lite affect to be somewhere in the middle, although I think we'll get something closer to the DS Lite effect than the 3DS XL one. Next week's numbers are going to be big ones; Very important ones for the Switch and Nintendo.

The other big factor in comparing these two launches it what happened in the weeks following the release of the updated version.  With DS Lite, the number kept increasing every week for a number of weeks following the DS Lite launch.  In fact, the 124,286 at launch was the LOWEST weekly number for many months following.  The baseline essentially tripled.  The 3DS XL, however, was a one-time spike that immediately came down each following week, only staying over 100K for the next 3 weeks.  After 2 months, the baseline was almost the same as it had been before.

I think we can all expect a big launch week for Switch Lite, but I'm very interested to see what happens in the weeks following as well.

The thing to remember with the DS and 3DS is the different circumstances and times of when they were released. 2006 was when handheld gaming was at its peak in Japan. The DS was selling monstrous numbers while the PSP was selling respectably well and on the rise. The DS had its peak year over there with around 8.4 million units sold; And then in 2007, it sold another 7.2 million units in Japan. No other system has come even remotely close those levels ever since, not even the 3DS, which peaked at a little less then 5.5 million units in 2012, the same year the 3DS XL and Animal Crossing: New Leaf came out. We've gone 12 years without a system reaching even 6 million units sold in Japan. The biggest culprit in that, by far, is the rise of the smartphone/mobile market which has led to the decline of the dedicated handheld market. Because of that, we are never going to see a system reach those baselines and levels of sales in Japan. It's never going to happen again. I expect the Switch Lite to raise the baseline, but not to THOSE levels.

That's depressing

As of this week's numbers, Mario Odyssey has sold over 2 million in Japan alone, making it the 4th Switch game to cross this threshold after Smash, MK8D, and Splatoon 2

https://gonintendo.com/stories/344936-super-mario-odyssey-sells-2-million-physical-copies-in-japan-alon

Next week will be interesting for sure

The difference between the Switch Lite and DS Lite is that the DS Lite was an objectively better version of the console to have. With the Switch Lite, you are losing a lot of the Switch's core features and limiting the amount of games you can play. Once things settle down I'm curious which SKU will sell better. I feel like in the US the regular Switch model will regularly outsell the Switch Lite, but maybe not in Japan.

Clearly some people are holding out for the Lite, as Switch sales have dropped in anticipation of this release.

It'll definitely be the better seller in Japan, everywhere else it's difficult to say. $199 instead of $299 is huge though.

Another difference is that the DS Lite essentially replaced the original DS, but the Switch Lite will continue to be sold alongside the OG Switch. It's like having two separate consoles being sold together, but both being counted as one console.

The lack of features will be made up for by the lower price point and improved portability. The base Switch will still account for most Switch sales when all is said and done, but there's definitely a place for the Lite as an entry level device. Now that 3DS is over, they need something to fill that cheap portable void.