According to a Google+ post from Motorola’s VP of Product Management, Punit Soni, he wrote that Motorola’s older handsets would continue to receive updates as well as long the hardware allowed it. His post was in reference to the new software features that would arrive in Motorola’s recent products.
However he adds, “And better still, all that software will come to all our existing users too (as long as the Hardware allows it)” Software updates have always been a contentious issue amongst Android owners and OEMs. There are times when OEMs would neglect older products due to hardware incompatibility, which is a stark contrast to iOS where products that are 3 years old are still eligible for the updates.
In any case hopefully Soni’s statement will reassure you that your current Moto X and Moto G handsets are still eligible for updates in the future, so if you’re not the type that upgrades phones every year when a new model is released, you should be set for a while.