How will a massive increase in hashpower affect orphan rates?
If the average time to find a block is T, and the typical time for a found block to propagate in the network is t, then the proportion of orphans among all blocks will be roughly 1/(1+T/t). As long as T>t there's not much risk for the network; however it could be a challenge for orphan-paying pools, for example If T=9t then 10% of the block rewards will need to be paid out of pocket.

If a PPS pool pays B/D per share, it is in fact using an artificially low difficulty - the difficulty metric measures how hard it is to find a block (orphan or not), when in fact what is relevant for calculating the due reward is how difficult it is to find a valid block.

If the network hashrate increases by a factor of X, then until difficulty catches up the average time for finding a block is (10 min)/X. I doubt the transition to ASIC will cause a discrepancy by a factor of over 10; this would give T = 1 min. With a conservative value of t=5 sec you will get about 7.7% loss for paying orphans. The actual numbers for both X and t will likely be much less (especially since concentrated hashrate lowers t), so I don't think the loss during the transition period will be prohibitive.