What do you guys think?

IMO I think Nintendo killed off the Wii way too early, for a good while it was the fastest selling console of all time. It eventually did slow down however I think if Nintendo kept supporting the Wii for 6 or 7 years they could still be profitable, way more profitable than their successor the Wii U at the very least. I don't understand why Nintendo rushed to replace the Wii so early.

Some of my theories of why they dropped the Wii prematurely is maybe cause Nintendo was so optimistic with the Wii U that they thought that it would sell so much more than what the Wii was selling at that point, or maybe Nintendo prioritized to be the first 8th gen system to market to have a year headstart against Sony & Microsoft, since the Wii U was aimed to appeal to more of the PS and Xbox gamers. Or maybe Nintendo wanted to release the Wii U early before smartphones and tablets became huge, as Miyamoto stated.

They certainly cut software support for it too soon.

After 2010 they dropped it like a rock, leaving it to coast on fumes for its last two years, and even handled the localization of games like Xenoblade, The Last Story, Pandora's Tower and Fatal Frame 2 very badly; all four should have seen timely worldwide releases.

A 2012 replacement wasn't too soon per se, but they should have at least supported it properly up until then.

Well I mean, the WiiU arrived only one year before the PS4 and X1. It seems to me they just wanted to be first out of the gate with their 8th gen console. With that in mind, I don't think it was ended too early at all. The WiiU failed for a number of reasons, but the Wii being ended when it did was not one of them.

As Curl-6 pointed out however, they did slack on the software front in the end of its life. I will agree to that.

No. The Wii craze was well over by 2012. Wii didn't have many notables in 2012 aside from Kirby 20th and Mario party but 2011 was its last year with interesting games. Xenoblade. The Last Story. Pandoras Tower. Zelda SS. Kirby in Dreamland. Conduit 2. Rayman Origins. Some good games to send off but I feel a lot of even third party was winding down for it. I think by 2010 I lot of people were expecting and hoping for at the very least a Wii HD, I believe there were rumors of it to be shown at E3 2010. 2012 was the right time at 6 years. The standard for Nintendo. Wii U's marketing sucked. Even if the marketing was decent I don't think devs wanted to support Wii U regardless. API was still Nintendo's. HD system which meant more risk. The CPU was ancient. It was 11 years old essentially. Wii ended at the right time. It's just their successor was a bad product.

My belief is that they didn't make enough motion control games.  The last really significant one was Wii Sports Resort.  This was released in 2009.  After that, their core fan base of motion control gamers didn't get a whole lot.  I think a lot of the games that were made to appeal to N64/Gamecube gamers were a mistake, e.g. Mario Galaxy 2 and Metroid: Other M.  Instead they should have doubled down on more motion control games.  They didn't make Wii U games to appeal to the Wii Sports crowd either which is the biggest reason why the Wii U flopped.

Wii HD, at 2010, would have been a much better story if it launched with SMG2

It ran its course imo

In terms of lifespan the Wii had the longest of any Nintendo home console in the west and in Japan it had the longest life of any console since the SNES. The issue of it not having games in it's last year is also very common for Nintendo consoles. The N64 and Gamecube already established the pattern of Nintendo basically dropping development of the outgoing system to focus on the next system in the final year.

I don't know how much the Wii would have had left in it if Nintendo had kept making games instead of switching over to Wii U development. While still good overall, sales were declining in 2010 even though Nintendo had an outstanding lineup that year.

The system I think Nintendo should have waited to release is the 3DS, at least by a few months. One of the reasons sales of the Wii U and 3DS tanked so badly right after launch was the lack of games. If Nintendo had waited until Ocarina of Time 3D was ready at the least the launch lineup would have been that much stronger and the wait until the next wave of games would have been much shorter, both of which would have helped the system build and keep its momentum while still allowing it to come out long before the Vita. The 3DS did recover from its initial struggles because of the price drop and a good lineup in the second half of the year, but that initial stumble I think killed its chances of reaching 100 million units sold, which I think would have been achieved if it both launched at a lower cost and did not have that initial drought after launch.

Nintendo was not able to provide enough support to their systems for 3 years. They didn't have enough games for the 3ds when it launched in the first half of 2011, though they managed to fix that by the second half of the year and kept it going for the next few years. They didn't have enough games for the Wii in 2011 and to an even greater extent in 2012, and the post-launch drought for the Wii U was legendary, with very few worthwhile games releasing in the first half of 2013. I don't think any release strategy could have saved the Wii U in the end given its price and the confusion in the market over it, but I do think it could have done Gamecube numbers of they kept some sort of momentum going with a decent release schedule after launch.

They didn't drop it too early from my POV. Instead, they waited too long to create a ""Wii HD". If the Wii U had released in 2009 or 2010 as a high res Wii, it would have been a beast. The Wii looked terrible on my TV. Even the shovelware on PS3 and 360 looked better. The Wii wasn't a "ten year machine". It had great software and a great concept but it was outdated even at launch.

Wasn't killed soon enough if you ask me, hate me for it! I'm sure they plan on keeping the Switch around for longer, they did with the 3DS even though it didn't sell as good as the Wii.