definitely it is due to Dorje Shugden issue that the Dalai Lama is not picking Trijang Rinpoche as his successor. i am sure the Dalai Lama would pick Trijang Rinpoche on condition that Trijang Rinpoche gives up Dorje Shugden. but it seems that Trijang Rinpoche is still not being seen around Dalai Lama recently, instead, Trijang Rinpoche is publicly seen with many Dorje Shugden lamas in Europe! so it is clear what Trijang Rinpoche's stance is, the position of "the Dalai Lama's successor" does not appeal to him, He (Trijang Rinpoche) chooses guru devotion (towards Pabongkha Rinpoche) over politics. A truly great being.