Hopefully it isn't just as broken as MCC at launch.
Something that helps is that some groundwork was laid with Gears 1 Ultimate Edition which probably would've been the most difficult game in the series to remaster both due to its age and the fact that two versions existed but the remastering work has largely already been done there.
Also, all the 360 Gears games run on UE3 and Gears 4 runs on UE4, both very well documented and commonly used versions of the Unreal engine, engines that team has a lot of experience with. Not to mention they can forgo doing the very cool but almost certainly a pain to implement switching between old and new graphics at the click of a button feature thanks to the original version of each game being BC. It's still a huge undertaking but honestly should go much more smoothly for the dev team.
Not to mention that if this thing was a disaster as they neared their planned launch date MS would delay until it was ready. The MS of now is a very different one from the one that launched MCC. An argument could be made that they may be more to blame for MCC launching in the state it did as I have a hard time believing 343 wasn't aware of issues and didn't try to communicate those issues to MS.
