Supposedly, Microsoft can and will issue OTA updates without carrier intervention or blocking. If this is true, it is a Good Thing.
Palm was the first to do OTA updates of the operating system, but the carrier could decide to block or limit deployment. As a result, many people (especially on Verizon) with Palm devices never received updates that fixed serious problems. I remember the Verizon Pre 2 never received Palm's last three updates to webOS for the Pre 2, which is outrageous, because Verizon said "we didn't have the resources to test them, and we won't allow them on our devices without testing." Pre 2 owners were literally stuck with bugs forever as a result.