I had the same offer and took it up. Actually, I think it is a great offer. You get free use of a virtually new Audi, fuel thrown in, your Q3 (when it comes) will benefit from a newer registration and therefore have a higher value. For me, it was a no-brainer, and I think a very generous offer from Audi given all the circumstances.
I think the bottom line with late delivery is a combination of higher than expected demand, possible gremlins in the production start-up in new factory, and component shortages (eg standard alloys, Stronic and probably more).
Finally, if you cancel, what then? Evoque's are similar leadtimes, and the problem (for me at least) would be that if I settled for my second choice, I would probably rue the decision in the months and years to come. So an Audi Q3 later this year with another Audi on free loan, or something not a Q3, that's the choice.