It sounds like they are rebranding The Pullman Hotel.

I was at the Mall of the Emirates just a week ago and didn't see any new construction, nor anyplace where they could do new construction. Furthermore, the Pullman hotel at the Mall has 481 rooms and is owned by Majid al Futtaim Properties, and per the press release:

"Starwood Hotels and Resorts Worldwide, Inc. and Majid Al Futtaim Properties have signed an agreement to open a Sheraton Hotel at Mall of the Emirates in Dubai. Scheduled to debut in the first quarter of 2013, Sheraton Dubai Mall of the Emirates Hotel will comprise 481 guest rooms including 94 suites, four restaurants and lounges and nearly 9,000 square-feet of ultra-modern meeting and event space.

The hotel will be directly connected to Mall of the Emirates"

And per the Majid al Futtaim Properties website:

"The Pullman is ideally situated on Sheikh Zayed road at the crossroads of old Dubai, the Marina district, Jumeirah beach and Business bay. The hotel features 481 upscale rooms and suites and links directly to Mall of the Emirates."