Gary Leff of View from the Wing reported on some insider information from SPG. Supposedly SPG's staff is being told that the program will remain a standalone program at least until the end of 2017. This is largely expected, as the integration is estimated to take 18 months and the sale won't close till around May of this year.
Further, SPG's Ambassadors have been told they'll be retained until the end of 2017, while there's a rumor that the SPG Ambassador program may even find a permanent home as part of the new Marriott Rewards program. Like everything else we've seen with this merger thus far, this is only speculation and should be taken with a grain of salt.