You might want to reconsider that response. If the answer were always "yes", then everything would be a member of your set V. For {{{}}}, don't you want the answer to be "no"?
The Axiom of Infinity does not define a set nor does it assert it as infinite. It simply asserts the existence of a set that satisfies two properties.
There is nothing in the Axiom itself to rule out an infinite set as a member. You couldn't imagine the set possibly containing {{{}}} as a member -- that was your error. Now you cannot imagine it containing an infinite set as a member -- again, your error.
Here it is, where N is not a specific set and also there are base members which are infinite sets.
∃ N ( ∅ ∈ N ∧ for any given x ∈ N ( ( x ∪ { x } ) ∈ N ) )
Definition: (x∪{x}) is called the largest successor in N iff (x∪{x}) does not have a successor in N.
Here is the bijective map between proper subsets of N, where for any given proper subset there is a distinct base member, and its other distinct members are defined according to (x∪{x}), such that no (x∪{x}) is the largest successor in any given proper subset):
Code:
N = {
∅, ---> {{∅}}, ---> ... <-- base members
{∅}, ---> {{∅}, {{∅}} }, ---> ...
{∅, {∅}}, ---> {{∅}, {{∅}}, {{∅}, {{∅}}}}, ---> ...
{∅, {∅}, {∅, {∅}}}, ---> {{∅}, {{∅}}, {{∅}, {{∅}}}, {{∅}, {{∅}}, {{∅}, {{∅}}}}}, ---> ...
... ...
}
Moreover, each proper subset has its own unique distinct members, since they are derived from their unique base member even though (x∪{x}) is a common property among N's proper subsets.
So N has actually two different properties that define any given proper subset of N, which are:
1) Distinct base member (where also infinite sets are base members).
2) A common form ( (x∪{x}) in case of this axiom ).
Since no proper subset of N has its largest successor, so is the case with the proper subsets of any given infinite member of N, which is one of its base members (the definition of the largest successor and properties (1) and (2) hold for any given set).
Moreover, since each proper subset of N has its own unique members (because they are derived by (x∪{x}) form from a distinct base member), we are able to define a diagonal set, which its members do not follow after the unique form of the members of any given proper subset of N.
But let's not forget that also this set (which is supposed to be a base member of N) even though it is not a member of any given proper subset of N, is indirectly defined by the definition of the largest successor and properties (1) and (2).
So, being closed under succession, is actually being closed under endless construction, which prevents |N|<=|N| as if N has all of its members, or ω as an ordinal number after all { |{}|, |{{}}|, |{{},{{}}}|, ... }