I dont think so? I have unlocked pluto and Aeris(?) but I haven't done anything much or explored every zone
Alright. The guy I'm talking about shows up every two weeks on one of the relays. You trade in stuff you got from the Void relics (if you chose not to use it to make the respective Prime items) for something called "ducats".
You spend ducats and a lot of credits to get rare goodies from this guy. Usually what people go after are skins and primed Mods. However... he DOES sell a quest for a Warframe, so you'll want to pay him a visit eventually anyway. (I think you need to be mastery rank 5 for that one?)
Be warned he's a snob - I usually visit him with Prime Warframes which makes him ease up a bit, but I accidentally approached him with a Gyre last time and his elitism showed big time.
I brought this up because the TennoCon Access packs let you visit a special relay, for a whole week every year (corresponding with that year's Access pack of course), where the entire inventory he's had for the whole course of the game's history is available for purchase.
You probably don't want to worry yourself with that until you're trying to fill in gaps after being a long-time player. It takes LOTS of ducats and easily millions of credits to get all of that at once.