What will you do if the RA is no longer appropriate and to continue to follow it will result in a collision? Keep following it? Or, do something about it?
Providing you are in a TCAS mandated environment TCAS will prioritise threats, better than you can. When the RA is no longer appropriate it becomes a TA with no further flight path commands so I can't imagine the scenario you paint.
Following the RA (until it downgrades to a TA) is your best course of action. Think of being under/overtaken on a collision azimuth from your rear quarter but with height separation by an aircraft you can't see (but TCAS can) but is currently no threat and receiving an RA for an aircraft you can see and avoid. The possibility exists that ignoring the RA commands (which would put you in the safest position) and operating purely visually could lead to a further RA on the unseen aircraft. It can and does handle multiple contacts quite well so by following the commands you will place yourself in the safest environment.