So if I keep playing to around 350 hours on my save file on Oblivion GOTY edition on PS3, I will encounter the A-bomb glitch?

yes

You might or you might not. There is no guarantee one way or another. Because no one really knows what causes it. It could also happen at 200 hours or less.

Unfortunately for you if you do get the abomb on the PS3, there is no fix, and you'd likely need to give up that character, and perhaps start a new one if you want.

Here is the current thread for the abomb, if you'd want more details:

http://www.gamesas.com/index.php?/topic/813915-slowfrozen-doors-fire-spell-etc-animations-thread-8-of-jittering-doorseffectsobjects/

Thank you for the informative post Savlian, let's continue this in the dedicated thread.