If they patented it in 2017, I'm guessing it probably didn't make it in to this one, but the assumption is that the next version may have that technology.

That's a good enough reason to pull it out, replace/upgrade the equip, and drop it back in with the new setup (new sources of energy), and if they get the whole thing to transmit wireless-ly with a 1% failures per 2 years (8 out of the 855 servers) then it's a truly set-and-forget thing. And they can be bringing them up every 2-5-10 years to replace/upgrade the HW and drop it back in.

One would imagine that the signal to noise ratio for wireless data transmission in the ocean would be pretty abysmal. That said, there's no reason why they couldn't just run a fiber optic cable out from it, as long as it's designed to rotate around said cable.

I thought of the cable solution, but that would have some wear and tear if the capsule gets to move around. I was imagining a periscope-y antenna, in the form of a buoy.

Short range high power wireless to cable. Basically cable but with a wear buffer.

Microsoft probably has enough money that they could leave the original one in, and pop down a new one with the new green energy.

(Of course, individual projects still have finite budgets.)

I assume that the project approved by the UK government specifies some requirements about environment protection and the fate of the material.

Building a new one would take more time

Yes, but they can build multiple in parallel.

It would need an antenna buoy as wireless does not transmit well in salt water.

If that was the reason, we'd know about it from the PR release. This must have been a failure.