"Hvad er chancen?"

Translation: What is the chance?

[stikuts]

Is this supposed to mean more like "What are the odds/probabilites?"
This sentence in English doesn't mean much to me

[deactivated user]

Yes, that's what it means. This sentence is often said when there is a very low probability of something happening.

"Jeg bliver professionel fodboldspiller en dag!"

"(Hvad er) chancen.."

EDIT: It can also be used when something very unlikely happens:

"Jeg har vundet en rejse til Mallorca! Hvad er chancen?!"

[stikuts]

mange tak

[-HKBK-]

Perhaps it just depends on where you are. To me (north GB) this is fine, although the plural is the normal way to say this: "what are the chances". And it's more like an exclamation of disbelief, rather than an actual question.