If there is an engaged clutch between the engine and gearbox (i.e. in a manual transmission, or auto with lock up), then the engine will continue to reciprocate faster and faster. A rev limiter may ensure a lack of fuel but it won't stop valve float (which even without combustion will still have an effect on engine braking), or your con rods from snapping from the increased stress due to the ever faster moving pistons applying larger forces to them. I don't see heat being a problem. If you kept the rpm very high and the conrods didn't break, then there is the possibility of the the valve springs fatiguing and failing, or without enough bounce, colliding with the pistons.
With just a torque converter, there is no direct connection between the engine and wheels, but the fluid will only allow so much slip, so you'll get the same problem, only it'll happen at a slightly (10%?) higher speed.