Per the Terms & Conditions (https://www.marriott.com/rewards/member-benefits/platinum.mi):
For Residence Inn and TownePlace Suites, upgrades from studio to 1- or 2-bedrooms are not guaranteed.
But maybe you'll get lucky.
"Are upgrades for Platinum Elite avalibale at Residence Inn's."
SaintsFan is correct. Officially, complimentary upgrades for Platinum Elite are honored if there is availability excluding Marriott Vacation Club, Residence Inn and Towneplace Suites. This pertains to paid or points.
Since Residence Inn and Towneplace Suites earn 5 points on the dollar, I find it more cost-effective to stay at these properties redeeming Marriott Rewards points. That said, if the Residence Inn or Towneplace Suites offers a PointSavers, requesting a comp upgrade through Platinum reservations can be effective. I've also found that if redeeming a standard award at Residence Inn, calling the hotel about a complimentary upgrade can result in minimal cash upgrade.
Basically, you have to throw the dice. Best of luck!
In an RI where I stay often, they will upgrade me prior to arrival.
However, on the "marriott odyssey" I just returned from, it was RI's refusal to upgrade to a 2 BR--called ahead and asked at the desk-- and then their disclosure that a rollaway was not allowed ("fire code") in the one bedroom suite I'd reserved and confirmed that led me to have to change properties and then be told an upgrade promised at the new property (CY) could not be given to me--even though the room was available--because I was on points.
I agree with another poster's report of properties picking and choosing which elite benefits to recognize--running into this more and more.
RI is popular locations, seem to get the blessing from Marriott that even if availability exists, upgardes are not "allowed" - bascially, what they are saying is that they pick and chose, which beneifts to give - as said by others--its a load of **** Many of the associates are told by property owners/manages that is the rule, so the respective associate is faststead and takes it at his word that there are no upgrades--same can be said at vacation clubs and now Towneplace Suites--its BS!!! Many of these properties refuse to upgrade based on points--they'd rather the room go empty--real pity.
The worst RI w no appreciation for Platinum Elties or any other elite, is RI Treasure Island, FL!!!!