Well, Juan Diego has "postoponed", ie canceled for the foreseeable future, his Madrid commitment and, perfectionist that he is, will not be singing in Rigoletto for quite a while. It is indeed a heavier role, much heavier and more potentially voice-damaging than expected. If he's not comfortable going ahead, and he clearly isn't -- the Lima tryout was just that, a tryout in a tiny venue, so the true test came in Dresden -- he's better off leaving the Duke alone for a few years.
For all the corporate pressure that he's under to tackle the heavier, more popular stuff -- not just the Duke... Rodolfo? even, may the Lord forbid, Alfredo? -- Juan Diego and Maestro Palacio are very right in erring on the side of caution and of vocal longevity. Too many examples -- even in very recent months -- of very bad choices made simply to appear in a heavier, popular role not right -- or not yet 100% right -- for one's voice.
OC enjoyed the live broadcast from Dresden, but she endorses our lamby prince's decision 100%.