Is there a way to see how many viewed my SyncSketch upload?

Yes, you can see how many users have seen it - unfortunately we don't yet show exactly who.  you can find the information in the Project Overview and within the Review Player.

From the Project Overview

Open the Media Pane for the Review containing the item by twirling down the arrow at the left of the Review header.

Switch the Media Pane to the Table View using the icon at the far right, as indicated below.

Now you can see the column with view counts (among other useful information) for each item.

From the Review Player

Hover over the (i)nfo icon in the viewer:GettingViewCount