edit: That said, as noted elsewhere in the comments, it's pretty pointless to speculate, especially when a linked article mentions more issues than just a wheel having come off. (Although it's not unreasonable to notice that in particular, seeing as an Air Canada Dash-8 dropped a wheel on takeoff just last month.)
Chances are they'll have that plane back up in the air in a few months in regular service unless it was right on the edge of retirement already.
Mitigating factors: Rear wheel brakes should still work. Reverse thrust can further help slow down the aircraft.
Given the response time of emergency evacuation + fire response teams, likelihood of mass casualties are low.
https://avherald.com/h?article=4c29e455&opt=0
https://avherald.com/h?article=4b92a56d&opt=0
"A spokesperson for Air Canada told Sky News: "Air Canada flight AC837, Madrid to Toronto, experienced an engine issue shortly after take-off. A tire also reportedly ruptured on take-off, one of 10 on this model of aircraft."
https://news.sky.com/story/air-canada-flight-returning-to-ma...
A similar 767 made a gear up landing in 2011 with no injuries. [0]
[0] https://en.wikipedia.org/wiki/LOT_Polish_Airlines_Flight_16