Thanks for the answers, but it didn't really answer my question.
The reason I asked, is if I were to use a VPS like digital ocean, with a smallish VM, would it fit the bill for a long time? or would storage be a concern? Performance I can work out, by creating additional VM's and delegating certain roles (DB, reverse proxy, fail-over, etc), increasing resources etc, but my concern is storage. As storage costs per GB.
Even if I were to go physical, how much HDD's should I get? Can I use SSD's (more expensive, less space, but higher performance), or stay with HDD (cheap, and more space, but lower performance)? Will 4TB be enough for the long term, or can I stick it out with just 512GB for another couple of million posts/users?
How much storage would 10 million posts with 1 million users (10 posts per user) work out at?
Maybe I should've elaborated in my first post ?