If the production numbers of X stays low (today's report says 10k/day), I highly doubt you will be able to get an iPhone X from a carrier, or even on the iPhone Upgrade Program.
Apple will try to control demand because supply will be so low. Price is one way to do it (we all know it's rumoured to start at $999), the other is to make everyone pay for the device upfront, which a lot of people won't be able to, and hence the demand will lower to match supply.
Since it's a special, anniversary, one-off model, I think you will only be able to buy it from Apple only, at least for sometime, and only if you pay the amount upfront.
Apple will try to control demand because supply will be so low. Price is one way to do it (we all know it's rumoured to start at $999), the other is to make everyone pay for the device upfront, which a lot of people won't be able to, and hence the demand will lower to match supply.
Since it's a special, anniversary, one-off model, I think you will only be able to buy it from Apple only, at least for sometime, and only if you pay the amount upfront.