I don't believe anyone serious enough to buy the 7D2 is likely to invest in long glass that won't mount up to a FF as well, even if such a lens were cost effective which (thanks) neuro has pointed out isn't really the case anyway. I suggest the target strategy for EF-S is pretty well established -- the highest quality EF-S glass is wide, and doesn't have the build quality that serious wildlifers would demand in their long glass. what that means to me is:
1. The 7D2 owner wishes to maximize the potential for sports/wildlife while investing in glass instead of a 2nd body. Such an owner will want to use/rent long L glass whenever possible, and will be happy to use EF-S glass for WA and UWA.
2. The 7D2 owner has a FF body as well, in which case the use of long L glass is expected anyway, and EF-S glass is not desired at all
3. More generally, the xxD and xxxD users are more likely to turn to lower cost third party long glass, not realizing that the higher density sensor demands more, not less, from the lens. I see Canon yielding this market to the third parties because it does not fit their reputation of leading absolutely in the high quality long glass department.