My guess would be yes...unless it is in too much shade then all bets are off ...Mine has also been in the ground for two years and shows no variegation...it does get afternoon filtered sun ... I personally think it is a really pretty tree even with out it but I assume mine will eventually show some but if not I really don't care (it's one less "burning" problem to deal with ;>)).
Everyone should always remember that those picture perfect photos you see in catalogues are there for a reason ...to sell the tree ...I would bet most don't ever look that good or only for a short period of time...and most likely vary from year to year except in the most perfect growing areas under the most perfect growing conditions..David

In Orygun, "Ukigumo" can be planted out in full sun and does quite well after getting established. But even here, it will throw green branches that normally revert to varigated the next year. The right coast is a much different world from here, but I would still question the validity of the plant if no varigation is noted in two years of growth.