Many users have reported that they are experiencing issues with the Forza Rewards system properly calculating their Rewards tally. Since the problems that plagued the Xbox Live servers had occurred, these problems with Forza Rewards have been quite prevalent. Unfortunately, this takes place at a time when many of the team’s engineers are very likely on holiday leave and maintenance may not be immediately feasible - hence, the problem persists.
For this reason and until we get official word for Turn 10 regarding the issues with Forza Rewards, I think it would be safe to recommend that users do not attempt to redeem their Forza Rewards on January 1st. This can cause several issues: a server which seems to already be undergoing difficulties may be further hampered by an onslaught of requests to distribute Rewards credits. Secondly, redeeming at this point may cause you to receive an insufficient or inaccurate credits total. Lastly, anything done on your end by redeeming Rewards may not be able to be undone by the team once a resolution is put into place.
By my count, there are 31 days in January which is ample time for the team to rectify the Forza Rewards issues and for gamers to redeem, receive and download their Rewards credits. For these reasons, I suggest you avoid redeeming your monthly Rewards until Turn 10 gives us the green light.