I agree that had Voldemort's attempt on Harry's life succeeded, there would be a very real and interesting issue re Neville.
Given all we know about Voldemort, I find it hard to believe other than that he would have gone on to murder Neville, as his fear and his need for control over others and any risk of his own death was so pathologically extreme.
He may revere pureblood, but certainly not any possible risk to his own mortality and power.
Does the sequence of events affect any of this? -- I'm thinking about what, if any, effect the torture-into-insanity of the Longbottoms might have on Voldemort's perception of danger. One presumes that happened before the attack on Harry, since the rebound of that attack defeated Voldemort the first time and, near as I can tell, marked the end of the first war.