What can be inferred about Syme?
Syme was under careful watch by the Party for conspiring against them while rewriting the English language; the Party used him for what they needed and discarded him when their needs were fulfilled.
Winston's earlier thoughts about how easily it would be to vaporize Syme are verified when he comes in and sees that the Chess Committee list of members was retyped with one less name.
After Syme completed his task for perfecting Newspeak, he was discarded like the old language. He was one of the men who frequented places where the previous leaders of the Party had frequented and also been vaporized; it seems ironic that the same thing happened to Syme as he seemed to follow in the same footsteps of the past Party leaders.
Syme finally had enough of being under the rule of the Party and abandoned his post in a similar fashion of going A.W.O.L.
Syme came to the realization that eliminating a language that had been around for ages was not what he wanted to take part in any longer; quitting was not an option he was privy to and the only other option was to abandon his duty without leaving a trace of his whereabouts.