What has Syme become? Why does Winston draw this conclusion?

Syme has become to open in his speech, saying things outloud that will be frowned upon by the Party. When Syme claims that Oldspeak will be obsolete by the year 2050, Winston almost replies, "Except for the proles," but stops himself when he realizes that it might be unorthodox to make this claim. Despite this, Syme sees Winston's point and argues that he is wrong. In his opinion, Newspeak will take over completely, resulting in a climate without thought. He exclaims, "Orthodoxy means not thinking - not needing to think. Orthodoxy is unconsciousness." Upon hearing this statement, Winston thinks to himself that Syme is too intelligent, and will eventually be vaporized for seeing too clearly and speaking too plainly.