We're launching in January with a dedicated server (quad core, 32GB RAM) on which we have a single VPS (with only 8GB RAM) - this gives us plenty of options going further, either I can set up load balancing, add resources to the VPS, make more of them with distributed concerns (database, app, session...), etc. And with Hetzner, it's also very cost effective, like 60 euros per month.
Not sure that is the best way to go, but that's how we'll roll.