Given that the GEO ring space is indeed finite & should be kept free of debris (even crossing one) at all costs I can imagine eventually reverting to the idea of large communication stations instead of individual satellites.
The stations will likely still not be manned will support automated & possibly even manned servising. It could look likey large truss, kinda similar to the one used on the ISS. Inside it would host power & fuel interconnects. Attached to it would be the communication payloads, solar power modules, engines and fuel tanks. Periodically a resuply/repair craft would visit, replenishing fuel & swapping any failed modules. Depending on your launch costs broken mpdules would either be tossed to a safe graveyard orbit or brought back (possibly to a LEO space station) for refurbishment.
The first steps of this might be already happening with the recently launched Mission Extension Vehicle:
https://en.m.wikipedia.org/wiki/Mission_Extension_Vehicle
The MEV will grapple a satellite that is low on fuel and will act as it's replacement propulsion unit. In this way it can serve at multiple satellites and ppssibly even serve as a tug for satellites that have failed & are are likely to fail soon, to make sure they reach the designated graveyard orbit.
And other similar & more ambitious missions are already planned and being built.