You seem to be distraught that the VDSL box, a currently used piece of hardware, once updated to a G.Fast Box, has a capacity of 1Gbps.

From the customer's point of view, this update and its resultant speed increase is a future event and could be announced:

After an update of the currently used VDSL box into a G.Fast Box, customers will enjoy a capacity of 1Gbps.

From the company's point of view, however, this is simply an established fact in the present tense. They tried it out in a lab somewhere. We've got this box, we do a firmware update and voilà, we've got 1Gbps capacity.

By the way, gets the capacity sounds very non-idiomatic.

You seem to be distraught that the VDSL box, a currently used piece of hardware, once updated to a G.Fast Box, has a capacity of 1Gbps.

From the customer's point of view, this update and its resultant speed increase is a future event and could be announced:

After an update of the currently used VDSL box into a G.Fast Box, customers will enjoy a capacity of 1Gbps.

From the company's point of view, however, this is simply an established fact in the present tense. They tried it out in a lab somewhere. We've got this box, we do a firmware update and voilà, we've got 1Gbps capacity.

By the way, gets the capacity in your suggested revision sounds non-idiomatic: will get does not, because, as you noted, have is statal, but get can be a process.