Now that Nintendo said they will end the Wii U online support in about 6 months, does this change when we feel the new hardware will arrive? Years ago I assumed they would replace it this year but we all know that won't be happening. I was thinking next holiday season made sense now but late spring is starting to make sense as they are cutting the last cord on the Wii U and 3DS.

I still feel they will release it in September 2024, with a potential announcement around May or June.

WiiU/3DS shutting down has nothing to do with next gen. They still have Switch games coming out next year, I don't see any reason they would release next gen early. Hardware sales are still pretty good and software sales are still great. Next Fall / holiday season seems almost certain to be when the successor will come out. Wouldn't be surprised at something like a September release though rather than waiting until November, so as to get both a big launch plus a separate holiday season.

I'm going to go with Early 2025 If the Switch is still being Supported to FY24/25.

Summer 2025 I fear
They wan to reach 170 million.

Nintendo has a reason to be cautious since their rate of successors faring worse outnumber the opposite outcome 2 to 1.

Still, most Switches sold nowadays and in the future are the OLED models, and likely as a replacement for current owners. The added manufacturing cost of the OLED model is unknown, but Nintendo assured costumers and investors that it's more than the $10 that was claimed by a 3rd-party report.

Now, the Switch 2 will feature a common LCD panel, and the cost of the T239 on the Switch 2 likely won't be more than $20 higher than the X1 (assuming $10,000 for a 5nm wafer vs. $3,000 for 16nm, and die sizes of 160 mm2 vs. 90 mm2).

While we don't know what other bells and whistles the Switch 2 might also come with, there's a real possibility it might turn as much of a profit as the Switch OLED does even if it releases for just $349. It's simply not cost effective to keep the Switch around for this long.

Nintendo would just lose money on the table.

Why do they want to reach an arbitrary 170 million? 

That's about 15 million more units than the DS and about 12 million more units than the PS2. If Nintendo is set on having the bragging rights of selling more units than the DS or the PS2 (unlikely they care enough), 158-160 million units would be enough for them. 

Summer 2025 isn't too wild, I suppose. But the writing is all over the wall for a March 2025 or sooner release. FY 24-25 seems nearly a lock at this point. While there is almost surely more unannounced Nintendo software, everything after Super Mario Bros. Wonder is a smaller title. Heck, the stuff between Pikmin 4 and Super Mario Bros. Wonder was pretty small as well (1-2 Switch, Detective Pikachu).

Metroid Prime 4 or an unannounced DK platformer seem like the only big things that could possibly be left on Switch. And for all we know, those could be cross-gen or only on Switch 2.  I don't think Nintendo making an all-new 3D Mario platformer for a system that will be over 7 years old by time it would release. 

This holiday season!

Mid 24

I had March 2024, but I’m changing it to Mid-Late 2024.

They can still support the switch until 2025 and release a switch 2 in 2024.

Basically what Sony has been doing with all their consoles.