If that ratio stays the same and number of consoles between the two is similar to previous gens we would see about a 70m/100m split. The former is a big if though.

I'd be shocked if PS5 sells as low as 100m. Even with supply constraints it's outpacing the PS4, I see no reason at this point why it would sell less lifetime. I expect the PS + Xbox base will grow this gen to accommodate two systems both hotter than their predecessors.

PS4 had everything to win, now I feel scalpers and limited supply are pushing everything to sell to the limit. I can see Xbox selling better than last gen but not PS5 when everything calm down. I expect this gen to sell better than their predecessors too.

At this point, I'd agree with you, but market changes can really impact sales. The N64 sold around 15.2 million units by March 1998, which was the first year to year and a half on the market (due to a skewed launch) making it Nintendo's most successful launch to that date, yet falling into a distant last place by the end of its generation. I wouldn't expect PS5 momentum to collapse in the way the N64 did, but I also wouldn't expect sales to be proportional to the PS4. Scarcity can also drive people to purchase a product earlier than they normally would - Nintendo's often accused of manufacturing scarcity to improve demand.

With the OLED-model out and expecting to do great, with another bombastic year in sales and most probably also a great 2022, I don't think the Nintendo Switch 2 (or however they will call it), will come out before 2024, my guess is 2025 as I think Nintendo will really push the current Switch models with quality and quantity software late into its lifetime (in opposition to all their former home consoles). They see how Sony and Microsoft are doing it, after one year on the market (and continuing well into the 2nd year), they both scarcely have any exclusive system-seller for their new consoles, almost all the big titles are cross-gen. Seeing that they are doing well with that strategy, Nintendo will do the same. In our age, gaming technology is scalable and this is a huge advantages over past generations, it would be stupid not to make use of it. The scalability could also be argued vice versa, that exactly because of scalability, the Nintendo Switch 2 will come earlier. But that's not realistic as Nintendo stated many times that they aim for a long lifecycle.

But the PS5's "scarcity" is more abundant that the PS4's. This is also reflected in software sales which are higher for the same period. Its true we don't know how PS5's life will progress, it may be more front loaded but I don't think scarcity makes for good reasoning. 

Second place, not last place (that title would go to the Saturn)

UK sales update for next week:

Nintendo Switch OLED UK launch significantly bigger than Switch Lite | GamesIndustry.biz

People are always doubting PlayStation sales potential. It happened last generation and PS4 kept breaking sales records. Every financial report shocked people and even upset some. The same thing is already happening with PS5 financial report's. It's pretty funny to watch.

There's really no reason why PS5 won't sell as much, if not more, than PS4. It's already selling more sales aligned.

You can't say it's because of supply problems increasing demand. The demand was already bigger than PS4's before it launched. Definitely not the scalpers excuses, software sales prove that. I see the other excuse was brought up too;PS4 had the generation easy. I don't think you realize how ridiculous that sounds. Sony's worse generation, the PS3, still saw that console selling 90M. The PlayStation brand huge. Now Bigger than it's ever been. An average generation for Sony is 90-100M. It's not logical to expect the PS5 to only sell 100M. Historical data tells us this is unlikely to happen.

Lastly, i see people mentioning Switch still outselling PS5 in it's lowest sales week. Funny how the supply contrained excuse is used for PS5 artificial high demand but it isn't used for the reason why Switch is currently selling more than PS5. I would think the console that's not readily available would naturally not outsell the other platform that is.

You should be wondering what PS5 sales are going to look like once stock is normal if sales are still this high with limited stock almost a year after launch.

...and slapping their faces each time.