I'm notoriously bad at guessing babynames and never even came close
soooo, i have a theory for next baby Tindall's name:
Mia and Lena are in dutch actually quite traditional names, even old fashioned; i think they'd probably be most associated with women over the age of 60 or 70. The pronounciation the family use is also very much how the names would be pronounced in dutch. Mia is a short form of the even more traditional Maria (Mary), Lena of Helena (Helen).
So, for the next baby, i'll go another couple of old fashioned dutch names that are still pronounceable in english:
Fred for a boy
Nelly for a girl