Microsoft has a lot of opportunity to either:
1.) see if some franchises deserve new entries from an interest perspective. Banjo, Killer Instinct, Age of empires, Blue Dragon comes to mind.
2.) try and build "good will" and re-establish fallen IP like Halo, by giving the other consoles the MCC. Or Halo 1-3 or whatever. This is critical. Halo could still be MS biggest IP and also a box office movie sensation. But the current view of Halo is bad. The TV show, Halo 5 launch, and Halo Infinite launch did the brand no favors.
3.) GAAS, games that could be GAAS across Consoles, PC, mobile, and iPad. Full House poker, (the rumored) World of Warcraft mobile, Guitar Hero and 1v100 come to mind immediately. These could be F2p or have monetization items such as commercials or season passes.
4.) Bring back a profit on smaller niche IP. Battletoads, Rare Replay, Halo Wars, Gears Tactics, Powerstar golf, psychonauts 1-2, etc.
5.) Finally. Just give everyone that canceled Goldenye XBLA game. That would be fun and an interesting gauge compared to their other FPS franchises.