This is like looking at a bowl of alphabet soup and trying to read it as a novel. It helps me to keep all the parts in place by doing this:
Marriott, Intl. - Acronym MI - Stock Symbol MAR = the Marriott hotel business
Marriott Vacations Worldwide - Acronym MVW - Stock Symbol VAC = the Marriott-affiliated timeshare business which was spun off from MI in 2011
Marriott Rewards - Acronym MR = the Marriott customer loyalty program affiliated with MI and MVW
Starwood Hotels and Resorts Worldwide, Inc. - Acronym SW - Stock Symbol HOT = the Starwood Hotel business which it has been announced will be acquired by MAR sometime in 2016
Starwood Vacation Network - Acronym SVN = the Starwood timeshare business which is in the process of being re-named Vistana Signature Experiences - Acronym VSE, and spun off to Interval Leisure Group, Inc. - Acronym ILG - Stock Symbol IILG, expected completion Q2 2016
Starwood Preferred Guest - Acronym SPG = the Starwood customer loyalty program affiliated with SW hotels and timeshares until completion of the timeshare spin-off and hotel business acquisition, at which time the affiliations will come under the MR umbrella in as-yet-to-be-announced form
When all is said and done as it's been announced so far, it should shake out as others are theorizing that the current Marriott and Starwood timeshare owners will have access to each others inventory only through cash stays by way of MI and customer loyalty points redemption earnings/stays by way of MR.
IMO there's a very good possibility that when the SW hotel business comes under the MI umbrella then the MVW Destination Club owners/members will be able to access them through the DC Explorer Collection, and possibly an ILG portal can open for certain VSE owners/members to similarly access MI hotel inventory.
Integrating the two timeshare companies could be done more thoroughly through the DC Exchange Company because its governing docs as written allow for such an affiliation, but there are still way too many moving parts that have to be set in place before that can happen.