One of the main reasons why the Switch is doing so well is that people love the idea of taking that same console game on your TV on the go anywhere. And imo I feel like it's really the closest thing we've seen thus far with the console gaming on the go idea, previous handhelds always felt a pretty big step apart from their console counterparts, but seeing how the Switch is able to handle these huge PS4 type games with nearly identical graphics is amazing.

However, cloud gaming has the ability to stream full console games anywhere on a smartphone or PC with pretty much the exact graphical fidelity as seen on a console and could be played on nearly every smartphone. With this in mind and if maybe Microsoft Xcloud or Amazon Luna blows up, how much could it threaten the Switch's success and appeal since Cloud Streaming services could offer the same main appeal that the Switch can offer?

IMO I don't think it'll affect the Switch's success much, most people are buying a Switch for the Nintendo games that you can't get anywhere else. I think only a small percentage of people really brought a Switch to play multiplats on the go, so I doubt cloud gaming will take a large percentage of switch buyers. Plus with cloud gaming portably you gotta worry about taking a gamepad with you on the go for an optimal experience and good internet connection, I don't really find that convinient compared to the Switch.

I doubt it due to latency/datacap issues

At some point probably, but as of now, the technology isn't good enough yet.

Do they have Zelda,Mario or Pokemon? No. So no.

No, different audience and you can't reliably play games in a car or on the train (I know).

Playing doom eternal on phone with kishi controller. No perceived imput latency.

The next Nintendo system is the one that is going to struggle more with this, if at all. Switch is going to be a little old when the Cloud becomes more commonplace.

No, I don't see it effecting Switch's success.

The Switch is a portable unit, primarily geared towards gaming, while mobile phones attached to the cloud are primarily designed around making calls, videos, texts and some general purpose apps, and then a small bit of gaming.

The Switch has already proven that there's still a userbase to cater towards, and so far mobile gaming hasn't really butchered it, and so far neither has Stadia, so I don't see Amazon doing it either.

My main concern is if Amazon does gain ground, and Stadia improves, then MS releases theirs, that we'll start seeing more competitors entering the ring. The last thing I want to see is more and more companies gearing up for pure cloud gaming, because I know normies will eventually just mass adopt that over time.
Switch is fine for now, but I think if Cloud gaming really manages to take off proper in a few more yrs, then gaming as a whole is going to evolve to that end point; always online gaming rentals, a gamer's worst nightmare, and a publishers orgasmic wet, long lost dream.

If anything Switch model is the least likely to be replaced by Cloud Gaming