According to job postings at Avalanche Software, the new installment may emphasize online mode. The developers are looking for engineers to create online systems. This could mean that the sequel will no longer be just a single-player RPG.
The job descriptions include terms "matchmaking" and "waiting rooms," indicating elements of competitive play. Rumor has it that the second part may feature multiplayer duels on wands and Quidditch matches.
It seems the publisher wants to turn the game into a service with constant updates and in-game purchases, including cosmetic elements. Although the first part was a single-player RPG, its success may prompt Warner Bros. to create something like a magical MMO, where players together explore the castle and its surroundings.
It is still unknown whether the online mode will completely replace the single-player game or become an option. Perhaps the studio is working on two projects simultaneously—a sequel and an online spin-off.