If Elijah did not die, then he had no need of reincarnation - his original incarnation would still exist. So the other part of the question is whether it was meant literally or not.
Although it must also be said that relying on John to accurately portray Jesus' teachings is a bit odd if you genuinely consider it untrustworthy.
And as a side note, the original reference to Elijah's return does not sound an awful lot like John the Baptist, and somewhat ironic given Matthew 10:35-36
Malachi 4 NRSV writes:
5 Lo, I will send you the prophet Elijah before the great and terrible day of the Lord comes. 6 He will turn the hearts of parents to their children and the hearts of children to their parents, so that I will not come and strike the land with a curse