Ven @Dhammanando already pointed out above that this logic doesn’t work (much to my surprise).
Thinking about it more, I realized I could use the same logic to argue that since the Buddha had been in saṃsāra forever without getting enlightened, it should therefore be impossible for him!
The trick is that enlightenment is not a random event and is therefore inappropriate to model as “a small probability.”
So, it could be that there’s a finite number of beings and we just happen to be in the “middle” of history: some day soon all the beings who could attain, will have already and no more crossings-over will happen after that (So you better get on the boat now!). This is an unpalatable conclusion given Buddhism’s general preference for cyclic cosmologies, but not necessarily an illogical one.
That said, I think that there are enough hints in the Canon (including this unpalatable “ultimate fate”) to suggest infinity that, for now, I’m comfortable holding the view that beings in Saṃsāra are infinite.
For me, you can only know about one being, and that is you. Each person’s samsara is their own. Each person has no real access to another’s samsara. How would that be possible? It’s all filtered through your own senses, so actually that’s your samsara, not theirs.
(For me) 1st watch revelation is about your own past lives and second watch revelation is about your own current life (watching the coming and going of what is perceived as “others”)
What one can say is that there’s not enough time in an individual iteration (birth - death) to recall all of the past iterations in any sort of detail to make a valid assessment.
So for me, there is precisely one being in samsara and that’s me. Luckily from a EBT perspective, that’s cool, because I can’t help you guys get enlightenment (until I’m enlightened), I can only help me. In fact you guys are probably all enlightened beings trying to skillfully help this dunderhead.
¯\_(ツ)_/¯ But that’s okay. Since you’re the “one being in samsara,” I guess you can define “being” and “samsara” however you like Have fun talking to yourself!
My definition of ‘being’ is anywhere that there is the perception of suffering arising and passing away. My definition of ‘samsara’ is wandering on from one life to the next. I don’t know if that fits with a valid interpretation the EBTs?
Can I ask you a couple of questions I wonder? … Through what else than the 6 senses do you know other beings? Do you think that an accurate picture of ‘other beings’ is made through the six senses?
The Buddha did speak about the “world” as being “this fathom-long body” on a few occasions. However, I don’t know if that was meant to be interpreted to mean what you’re implying. Honestly, your interpretation sounds a bit more like Mahayana Yogachara philosophy than anything else to me. The Buddha did speak about the suffering of others, and always included others’ suffering when talking about negative actions (things that harm others, yourself, or both). Compassion, which is about other’s suffering, is central to the Buddha’s teachings in the EBTs, so I’d be wary of taking your idea too far.
I think in most Indian exegetical traditions these statements were taken as a shorthand way of expressing the moral nihilists’ belief in the kammic fruitlessness of filial piety, rather than assertions that one’s mum and dad don’t exist.
Indeed all ten of the propositions that make up mundane right view were understood to be just variant ways of asserting kammasakatā, the doctrine of ownership of kamma; while their contraries were understood as ten ways of asserting either moral nihilism (natthikavāda), kammic inefficacy (akiriyāvāda), or haphazardism (ahetukavāda).
I think if someone was a bona fide solipsist (as opposed to one who just adopts solipsism as a pose in a philosophical debate) and truly believed that his parents existed only in his mind, it might be closer to the Vinaya’s definition of insanity (“when their mindfulness is entirely forgotten and they don’t know what fire, gold, excrement, and sandalwood are”) than the Suttas’ definition of wrong view.
I broadly agree with what you are saying here, and note your word of caution… but given my understanding of ‘being’ …
… then how can compassion not arise when ‘beings’ are only the arising and ceasing of suffering? All these ‘beings’ appear to be trying their hardest not to suffer - making all sorts of strategies for a continuation of existence that brings only happiness - and yet, there they are, failures each and every one - little bundles of dukkha.
I feel that maybe the quote of mine:
has been taken out of context with the rest of the post. So I feel I have been misrepresented. One requires the rest of the post to understand that quote, and the post needs too be taken in its entirety, rather than just taking a few words from a sentence and arriving at solipsism.
This is quite possible, as long as you are interpreting Mahayana Yogacara philosophy correctly. As I understand it, Yogacara is not incompatible with the EBTs?
If we include the preceding two words of that (nested) quote, we see additional beings implied…
For you there is precisely one being in samsara and that’s you
For me there is precisely one being in samsara and that’s me
For Seth Meyers there is precisely one being in samsara and that’s Seth Meyers
For x there is precisely one being in samsara and that’s x
That’s not looking like solipsism. I took it to mean something like “whether the number of beings be finite or infinite, one* can only ever experience it from one’s own p.o.v.”
Have fun talking to yourself! 
