I would expect the TVM system to be replaced with ETCS at the next upgrade (which will likely coincide with the replacement of the Class 9s). However ETCS in the Tunnel isn't going to happen until LGV-Nord has been converted (AIUI the contracts for the resignalling of LGV-Nord have been tendered but not sure exactly what the status is).
If freight stays at 120kph then the value of raising the tunnel beyond 160kph is very low, as freight paths become even more disruptive to capacity. The tunnel has a 3 minute headway, so if a train is 10 minutes faster it will need to enter the tunnel 13 minutes later to travel at full speed through the tunnel, and no train may enter in between those trains.
(50km @ 100kph/60mph: 30', 120kph/75mph: 25', 140kph/87mph: 21'25", 160kph/100mph: 18'45", 180kph/112mph: 16'40", 200kph/125mph: 15')