Well read what you wrote.
Don't need to, I wrote it. But...
do I really have to explain this?
I said if it helps their bottom line, other retailers will use Amazon to deliver packages. That was strictly in response to
@Limper's post I quoted saying that other retailers hate Amazon and would never use a carrier associated with them.
You extrapolated from what I wrote, and it appears that you think I was saying that other retailers would use an Amazon carrier exclusively. I never said that, never implied it. The point I was countering was that other retailers would never use Amazon.
To continue to beat a dead horse, because I'm in the mood, I said "if... it is better for their bottom line". Follow that logic out to its conclusion. In your scenario, Amazon would be unable to staff up enough (not even mentioning building the infrastructure) to handle all of the volume of other retailers. If that is the case, shipping all of their orders through Amazon would necessarily not help their bottom line, so they would not do that. The concept is so simple and obvious it should not even need to be brought up. Thus, what you wrote had no relation to my comment.
All of that is not to say that if Amazon were to be successful running a carrier service on a small scale that they couldn't expand over time. I doubt they could get to a point where they were shoulder to shoulder with FedEx or UPS any time in the next 5 years, but beyond that, it's anyone's guess.