Whoever it is, what we'll have to do is be open-minded, supportive, and accepting over the recast.
Nobody will be like Kevin, but keep in mind, Kevin wasn't even the first to perform Elmo, Elmo was passed on to him by a fed up Richard (who inherited Elmo after Brian's departure). Whoever takes on Elmo now will need the same kind of consideration we gave Steve when he took on Kermit and Ernie, likewise Matt as he takes over Jerry's characters (and how he's already done an excellent job in proving to us that he'll be able to carry on Big Bird should anything happen to Caroll, God forbid).
Plus, we're just only in Season 43 right now, right? And they're current in the process of filming 44 at the moment, correct? Well, we won't be seeing 44 till next year, so we probably won't notice any kind of change or difference in Elmo for a couple of years or so, at the most.