[Mithadan]

It does seem that JRRT was leaning towards a Mannish origin for Orcs later in his life. It just isn't clear that he made a final decision on this issue. Further, a Mannish origin would have at least indirectly contradicted LoTR. While this could be solved by a new modified edition, it always seemed to me that he hesitated to change what was already published.

The conversation between Gorbag and Shagrat about "the bad old times", seemingly referring to a distant past is well known and often cited. Less well known is the age of Bolg, son of Azog. Azog was slain in the Battle of Nanduhirion in TA 2799. His son Bolg was slain in the Battle of Five Armies in TA 2941, 142 years later suggesting that Orcs were at least long lived, indicating at a minumum a partial Elvish origin.