Hybrid approaches are also really good, but I'm gonna be honest: If capital is not an issue and the growth is to be expected, I wouldn't steer into dedicated server region. It's just such an headache if it's not the core business
Dedicated servers are way less of a headache than cloud in my experience. Unless you are talking about buying and building your own hardware, which is a completely separate thing and not generally recommended. You can lease dedicated servers these days as easily as launching a cloud compute instance but way less than half the price. I pay around $265/mo for 32 cores and 128gb of ram with local, dual, mirrored 1tb SSD drives. Looks like a reserved instance with similar performance on AWS would be somewhere around $700/mo.
We'd likely have to have some reserve just in case our marketing and product do so well that the next peak of the load rises higher in absolute terms.