How to make force:navigateToSObject to open record in new tab

Yes, You can navigate to new tab using-

<aura:handler event="force:navigateToSObject" action="{!c.navigateToRecord}"/>

navigateToRecord : function(component , event, helper){
    window.open('/' + event.getParam('recordId'));  
},

Since Salesforce suggests not using hard-coded or dynamic URLs, I would recommend using the more reliable lightning:navigation to open a new tab in Salesforce. I struggled with solving this at first, so here is my working solution. Hope it helps.

.cmp file:

//include this anywhere in your .cmp file
<lightning:navigation aura:id="navService"/>

controller.js :

//call your method/action
onClick: function(cmp, event, helper){
    var navService = cmp.find("navService");
    var pageReference = {    
       "type": "standard__recordPage", //example for opening a record page, see bottom for other supported types
       "attributes": {
       "recordId": recordId, //place your record id here that you wish to open
       "actionName": "view"
        }
    }

    navService.generateUrl(pageReference)
    .then($A.getCallback(function(url) {
      console.log('success: ' + url); //you can also set the url to an aura attribute if you wish
      window.open(url,'_blank'); //this opens your page in a seperate tab here
    }), 
    $A.getCallback(function(error) {
      console.log('error: ' + error);
    }));
}

According to the docs, pageReference supports opening:

• Lightning Component (must implement lightning:isUrlAddressable)
• Knowledge Article
• Login Page
• Named Page
• Navigation Item
• Page Object
• Page Record
• Page Record
• Relationship Page
• Web Page