Besides "ageless" characters like Elminster, Halaster Blackcloak (Mad Mage of Undermountain), Trobriand the Metal Mage (whose spirit is in an iron golem), Laeral Silverhand (the Open Lord of Waterdeep), Szass Tam (Red Wizard lich lord), Manshoon, Malchor Harpell, etc. and other iconic characters like Volothamp Geddarm (trapped by an imprisonment spell and released after a century), we can safely presume that very many Halruaan wizards must have survived, as Halruaa could foresee the upcoming turmoil and managed to disappear from the surface of Toril before the Spellplague struck. Furthermore, we can expect to encounter elven wizards from Evermeet, a century being not such a long time period in their lifetimes, and the island simply having been pushed into the Feywild by the Spellplague.
It is also quite conceivable that some "heroes" of the very many FR tables from all around the world are still around. High-level wizards can have clones, can stay in stasis, can achieve undead status, can travel to the planes, can travel in time etc. to survive.