Currently, all lands above 1200 feet (the Upper Lands) in West Vancouver are dedicated as land under a 'Special Study Area' by West Vancouver and Metro Vancouver. Theoretically, if 50% of the MVRD Board agrees to the change (and West Vancouver wants it), the Upper Lands could be rezoned for housing. This as been a key sticking point for West Van to both agree to the RGS- this is despite their own studies recommending against the idea.
https://westvancouver.ca/sites/default/files/dwv/council-agendas/2015/jun/22/15jun22-5.pdf
Map of the area (the Upper Lands are the massive area in red in West Vancouver):
The reasons for not developing the area are largely environmental, but there's also a significant impact on the views of the NS mountains.

The suburban section could potentially go all the way up to the beginning of Cypress Mountain's plateau peak- or about 800 meters above sea level. (The ski resort is at 1000m) Most of the treed section in the image may be removed if development is allowed up to Cypress Provincial Park.
On the other hand, the amount of land up there is enormous.
But the maximum possible amount of land (including Eagle Lake and any other new potential parks) is about 17.97 sq km or about 4440.5 acres. To put that in perspective, that's larger in area than New Westminster. Additionally, much of it is still owned by the British Properties, making turning the entire thing into a park require a ton of money- if they even want to sell, rather than keep whispering into West Van's ear to develop it. They've been holding for nearly a century at this point.
It would reduce land pressures on the agricultural, rural, and industrial lands in the Fraser Valley- which was actually why some early Vancouver planners wanted to develop up the mountains- to leave the Valley pristine (impossible to do that now, but still, the point stands). If densification can't proceed fast enough (something Vancouver isn't great at), Vancouver is going to inevitably gobble up more of the Valley outside the Containment Boundary. Is sprawling up Stave Lake or Silver Valley that much worse?
It's also important to note the 1200 ft boundary seems to be an unofficial limit for Metro Vancouver as a whole. If the Upper Lands get developed, expect the precedent to change- and other areas above 1200ft outside parks to get developed eventually (like Mount Fromme and parts of Eagle Mountain)
So should the area be developed? Part of it? Or should the area be kept as undeveloped parkland? Is that even likely?