Hi,
I took the ride from Paris Est-Vienna on 21 May 2010, not exactly like yours from Paris-Munich, which is direct on a CNL. Depending where your hotel is located in Paris...if your hotel is in the Gare du Nord area, where I always stay, I would be very surprised indeed if the hotel didn't allow to keep your luggage there after you've checked out at 11 AM. That's the advantage of staying at Gare du Nord instead of on Rue Cler, the Marais or Montmarte so you don't have to store the luggage in a checked in locker or waste time on the Metro going back to the hotel. Staying at Gard du Nord means within 2-10 mins. max you are at Gare du Nord or Gare de l'Est with your retrieved luggage.
To answer your question, you have to check in your luggage at Gare du Nord and at Gare de l'Est, no more coin lockers as was the case 30 years ago at Gare de l'Est, before it was remodeled and refurbished.
The trick is to stay in the Gare du Nord area if you're taking a night train to Germany.