I actually ask that exact question to the reps at Attitash booth during the Boston Ski show this year. They were exploring the idea back in 2003 with USFS, with the possibility of expanding behind the Summit Triple boundary on Attitash, but it fell to a grinding halt. The reps think is was because of the environmental impact the expansion would have caused on that area, though no EIS was ever conducted by Attitash and submitted to the USFS for review.
I definately know the plans do exist, Les Otten had them displayed back in 1992 or 93, just after the Kachina Chair opened on Bear Peak. The plans were to expand into the bowl area and create a trail & lift system that would wrap around that entire. It consisted of 3 or 4 lifts, with an increased vertical from the back peak on the ridgeline.
The unfortunate part was the display was taken down very quickly because year later, the display was gone when I returned there to ski.
I agree the terrain back there looks awesome, but alot of blasting and slope stabilization would be needed to preserve the natural water drainage in that area. It is sounds similar to the reason Mount Snow & Haystack were never connected. The restrictions limited expansion above 2500' in elevation to keep the Coldbrook stream at a class "A" water quality standard. I'm wondering if that might the case here too because of the natural drainage system runs down between Attitash & Bear Peak.
It seems that the Coldbrook is no issue now since new owners bought Haystack, there is a major change going on there, more impact. On natural area. Were are all the evio's now?