Well considering that the Endevor tower was a single building with hotel/office component and it would have been 46 floors (imagining a 46 story office tower in Austin
), if there's going to be two towers with Trammell's proposal, I'm having a hard time picturing 650K possibly more for the office tower portion with only 40 stories.
Looking at the Endevor footprint, it takes up half the block. With two towers, each footprint would have be 1/4th of the block assuming that the plaza will stay. It doesn't add up so I think it's quite possible that the office tower will have more than 40 floors.
Hopefully we will get to see renderings before too long.