It is hard really, to see where the TGIE will sustain or continue after the passing of the Dalai Lama. Many of the younger generation (from what i have read and observed and also learnt from talking to a few Tibetans) is that many of them aren't really that interested in these old politics. Tibetans are now all over the world anyway, from Switzerland, to various parts of Asia to America and they are aligning themselves more and more with the citizenship of those countries. Many aren't even born anywhere near Tibetan communities or the TGIE.
It is interesting when you go to Tibetan forums or even when you meet Tibetans - many of them don't really talk about the politics (and those that do, don't really make sense or talk with any sort of logic, and usually just seem very fanatical); they just want to live their lives, especially the younger generation. Even with all the ban of DS there is a large and substantial number of Tibetans who don't want to get involved in commenting or taking sides. As they are living away from the central hubs of India and Nepal, it's not really a problem for them to continue to practise anyway, so they just continue to live as normal citizens of whichever country they're in.
Anyway, if we're looking towards spiritual guidance, it certainly won't be TGIE, that's clear!