Will there be an issue if my travel in the Schengen area is December 5-15 and I have a travel insurance (50,000 Euro coverage) for December 5-25?
The requested insurance for the Schengen visa is a minimum, you can be insured for more or for longer or even both at the same time.
There will not be a problem with your longer insurance.
My stay in the Schengen is from Dec 4th to Dec 6th. However I have got an insurance for 13 days. I am not sure if you are asking this question from a visa application point of view, but I got my visa successfully from Austrian embassy using this insurance.