I'm starting to get curious now on why people are so adamant on determining if it's a pro or successor. Let's play out some hypotheticals:
The rumoured specs are 100% accurate. Impossible ports now made possible. Elden Ring coming to the next Switch in early 2024. Fall Guys now runs either 1440p60 or 4K30 based on performance or graphics mode option. Regardless of whether it's a pro or a successor, you are going to be inclined to purchase it (especially given we're all on a Nintendo enthusiast forum).
If Nintendo markets it as a pro, does that disappoint you? That after six years on market, it's still not an even more substantial leap than what it already is? Capable of AAA titles using modern graphical wizardry to provide you upscaled 4K content nigh imperceptible from native 4K images, taken on the go to improve IQ on the 720p screen so you more frequently experience a rock solid 30/40*/60fps game? (*In this scenario I hope the screen offers this refresh rate, just roll with it)
If Nintendo markets it as a successor, does it excite or frighten you? Yes, this beast of a machine is ready to stand toe to toe with Xbox Series and PS5 consoles. It will still receive the same games like before if it were a pro, and those same games will still likely be delayed a year or more after release like before on the other consoles (Alan Wake, Life is Strange, Elden Ring, etc.). A successor is more likely to ask for a higher price tag though, far more than a pro revision could.
Or is it, at the end of the day, a desire to simply know more than what Nintendo/Bloomberg/insiders/leakers are currently offering? Just to set your expectations that for a portable device that as of 2017 has more than a million times the RAM and harddrive of the Apollo Guidance Computer?