Bungie have recently recopyrighted "Marathon Infinity" suggesting their next IP will likely be another Marathon game.They haven't copyrighted a Marathon title name since 1996

https://cocatalog.loc.gov/cgi-bin/Pwebrecon.cgi?v1=2&ti=1,2&SEQ=20200228144748&Search%5FArg=Marathon%20Infinity&Search%5FCode=TALL&CNT=25&PID=2TAgejCmYLw_chrwKH_wOBonlEMt0d-&SID=2