Can anyone envision a scenario in which Tom would be killed?
For example,let's say when Tom is offered the job in Vegas,he takes it. Would Mike see this as a betrayal or even as a possible liability in the event that Hagen got caught up in something,and was pressured to flip?

On the other hand,what if after a few more years under Mike's rule,Tom can no longer live with his own complicity in so many heinous acts(the killing of the innocent hooker,the murder of Fredo,to name just two)that he decides to retire from the Corleone business and go into his own law practice.

Of course there are a lot of possibilities for Tom,but the bottom line is,would there be any justification in Mike's eyes to warrant getting rid of him.

If one is willing to murder one's own flesh and blood for a real or imagined provocation, then anyone can be a target.

That is exactly what I envisioned if Tom had taken that job in Vegas.
Tom had a lot of incriminating information on Michael. He would have taken Tom's leaving as proof of disloyalty and dissatisfaction. The Law would have seen it that way, too. They would have pounced on Tom as soon as they found out he left Michael. Michael would never have risked it--Tom would have been a dead man.

And, as Oli points out, pithily, a man who'd have his own brother killed wouldn't hesitate to kill anyone else. Michael said as much to Tom in the boathouse: "If history proves anything, it's that you can kill anyone." He was talking about Roth and Pentangeli, but I don't doubt that the message was aimed at Tom, too.

I think that even if Tom would have stayed with Mike,given Mike's paranoia and his need to be perceived as a ruthless leader,Tom's days were numbered.
When Tom asked Mike "Do you have to wipe everybody out?",or words to that effect,the die was cast. He should have kept it to himself. Not only was it disrespectful,but to say it in front of Rocco served only to embarrass Mike.
I'll bet that at some point,Tom,(overestimating his "value" to Mike),would have lost it and confronted Mike about a lot of his decisions,especially his murder of Fredo.

It's a shame Tom wasn't in III. What a great character arc we could have seen.

Michael let Tom go? Following on similar thread

Crazy! offering Tom a job, poaching? him from Michael