As of beta.6:
If you don’t want the nativeElement but rather like to have the Ionic/Stencil object/component, do as you displayed
@ViewChild(Toolbar) toolbar: Toolbar;
if you do want the ElementRef respectively the nativeElement do as following (the read attribute is the key)
<ion-toolbar #myToolbar></ion-toolbar>
@ViewChild('myToolbar', {read: ElementRef}) toolbar: ElementRef;