For tickets issued on February 5, 2018 or after, Qatar Airways flights that have been upgraded with Qmiles or Qpoints will not receive all of the benefits of the upgraded ticket.
First off, upgraded tickets will not receive an increased baggage allowance. You’ll only be able to check as many bags for free as your originally purchased ticket allows.
You also will only have access to the lounge for your originally ticketed class of service. That means if you upgrade from economy to business class, you will not get access to the Al Mourjan Lounge in Doha. If you upgrade from business class to first class, you will not get access to the Al Safwa Lounge in Doha.
This is a pretty big move by an airline and definitely will reduce the value of upgrading to a higher class of service with Qmiles or Qpoints.
Luckily, you’ll still able to access Qatar’s lounges with award bookings.
Check out this Flyertalk thread for further developments.