Of your "young core," I say there are two, maybe three keepers there at most. I think it will take 4-5 years at the least to become a legit contender again, and that is if Ainge is actually able to get "impact" players in the draft.
Could definitely be true. You have to find out who the young core will be, what they will or won't develop into, etc. Regardless, the next step of the rebuild is wide open.
What could some of your firsts added with Young net you ? 2016 Brooklyn first + James Young ? How about a first & Sullinger ? Olynyk + your own first ? etc.
Determine the value in the market, see if it's worth giving up, or not. That core is so young that it's way to early to put a final grade on each talent. Some GM's might value them more than others, & that's where a GM has to put in his work. Determine that value.
You have options. You can keep who fits your system and send out others with Picks to up their current value. You could also develop some of these youngsters and turn them into an all star yourself. It's too early to tell with some of them.