Probably not a sinkhole yet. If it was there would be more heaving and cracking in the asphalt in a more semicircular pattern around it. Asphalt, despite its hard feel and appearance is not really a solid. It's a viscoelastic material, which is part of the reason why they use it to make roads. It is extremely viscous at normal ambient temperature and is elastic, meaning it will go back to it's set shape. But when you lay asphalt beside concrete like this, you get these kinds of holes because the two materials expand and contract at very different rates. Asphalt will expand and contract more than concrete so the edges like this tend to crumble away over time from wear and tear from vehicles or snowplows. The road base around the streetcar tracks is actually quite far down and the asphalt layer itself quite thick. Likely they'll patch it up before the snow flies so ice buildup doesn't pull away more of it.