|Tomppa Venture-Lieutenant, Finland—Turku|
It probably does not work. Wild Shape is not a spell, and Tenacious Shifting specifies it affects spells. In fact, Wild shape isn't even a spell-like-ability, it's a supernatural ability and other things that would affect spells (like dispel magic) don't affect it either.
That being said, as Paul pointed out, it has a 1-hour-increments duration so adding 2 rounds to that seems inconsequential anyway.