We also just returned from RM last Friday. I took a few walks past Breathless and looked closely at the construction and would agree that it doesn't appear that it could possibly open by its scheduled opening date, which is now April 1. However, as most of the rooms and other facilities have been closed in, they can literally work around the clock for the next 5 months. Obviously there's also a tremendous amount of outdoor work to be done as well. But AM Resorts is a large hotel operator and a good one (we've stayed at a few Secrets resorts in the past and toured Breathless in Punta Cana) and reservations are being taken beginning April 1. It has successfully opened many new, large resorts in the Riviera Maya over the last several years so I wouldn't discount the company's ability to open this resort on time. Opening specials notwithstanding, would not consider staying at a new resort for at least 6 months after opening, but that's another issue.
In terms of its impact upon Desire RM, it appears that only 5 or 6 rooms out of the entire resort will have a partial view of the end of the pool and pool deck, and those guests would have to be on their balconies to do so. Desire could probably erect some additional screening to block those views, although the palm trees around the pool would do the job if they were higher. But the construction of the swimup bar and the expanded Tentazione restaurant blocks a lot of the sight lines to the pool and pool deck from the nearest Breathless building. So I don't think it will have much of an impact.
There was minimal foot traffic along Desire RM's beach during our week (Oct. 23 to 30). Two primarily reasons are the seaweed issue making walking along the beach difficult in spots, and the sand groin jette that Desire installed at the southern end of its beach. The drainage channel that discharges water from the mangroves is along the jette, and a lot of beach has eroded on the Breathless side. So you literally have to jump off the sand groins to go from Desire to Breathless, and it is even more difficult to go from Breathless to Desire, as its not easy to scale that groin. So unless that situation changes, and it could, its going to really impede foot traffic across Desire's beach from Breathless and the other large resorts to the south, namely Azul Sensatori and Secrets Silversands.