TITLE: Is it true that $\lim_{n \to \infty} {(P(\forall i,j\leq n \text{ } [X_i, X_j] = e))}^{\frac{1}{n}} = P(X_1 \in Z(G))$?
QUESTION [7 upvotes]: Suppose $G$ is a group. $\{X_n\}_{n = 1}^{\infty}$ is a sequence of i.i.d. random elements of $G$ satisfying the condition that 
$$\forall H \leq G, \qquad P(X_1 \in H) = \begin{cases}
   \frac{1}{[G:H]} & \quad \text{if $[G:H]$ is finite}\\
   0  & \quad \text{if $[G:H]$ is infinite}
 \end{cases}$$ 
Is it true that
$$\lim_{n \to \infty} P(\forall i,j\leq n, \ [X_i, X_j] = e)^{\frac{1}{n}} = P(X_1 \in Z(G)) \ ? $$

What have I tried so far?
If we accept an additional supposition, that the events $\{\forall i \leq p, \ X_i \in C_G(X_p) \}$ and $\{\forall i \leq q, \ X_i \in C_G(X_q) \}$ are independent for any natural $p \neq q$. Then we can see, that
$$P(\forall i,j\leq n, \ [X_i, X_j] = e) = \prod_{i = 1}^{n} P(\{\forall j \leq i, \ X_j \in C_G(X_i) \}).$$
Now, let’s see, that on one hand
\begin{align*}
&P(\{\forall j \leq i, \ X_j \in C_G(X_i) \}) \\
&= P(X_i \in Z(G)) + (1 - P(X_i \in Z(G))P(X_1 \in C_G(X_i))^{i - 1} \\
&\leq P(X_1 \in Z(G)) + (1 - P(X_1 \in Z(G))\left(\frac{1}{2}\right)^{i - 1} \\
&= \frac{1}{2^{i - 1}} + \left(1 - \frac{1}{2^{i - 1}}\right)P(X_1 \in Z(G)) \\
&= P(X_1 \in Z(G))\left(1 - \frac{1}{2^{i - 1}} + \frac{1}{2^{i - 1}P(X_1 \in Z(G))}\right)
\end{align*}
and on the other hand
\begin{align*}
&P(\{\forall j \leq i, \ X_j \in C_G(X_i) \}) \\
&= P(X_i \in Z(G)) + (1 - P(X_i \in Z(G))P(X_1 \in C_G(X_i))^{i - 1} \\
&\geq P(X_1 \in Z(G)) + (1 - P(X_1 \in Z(G))P(X_1 \in Z(G))^{i - 1} \\
&= P(X_1 \in Z(G))^{i - 1} + \left(1 - P(X_1 \in Z(G))^{i - 1}\right)P(X_1 \in Z(G)) \\
&= P(X_1 \in Z(G))\left(1 - P(X_1 \in Z(G))^{i - 1} + P(X_1 \in Z(G))^{i - 2}\right)
\end{align*}
So, we have
\begin{align*}
&P(X_1 \in Z(G)) \\
&= \lim_{i \to \infty} P(X_1 \in Z(G))\left(1 - P(X_1 \in Z(G))^{i - 1} + P(X_1 \in Z(G))^{i - 2}\right) \\
&= \lim_{n \to \infty} \left( \prod_{i = 1}^n P(X_1 \in Z(G)) \left(1 - P(X_1 \in Z(G))^{i - 1} + P(X_1 \in Z(G))^{i - 2} \right) \right)^{\frac{1}{n}} \\
&\leq \lim_{n \to \infty} P(\forall i,j\leq n, \ [X_i, X_j] = e)^{\frac{1}{n}} \\
&\leq \lim_{n \to \infty} \left( \prod_{i = 1}^n P(X_1 \in Z(G)) P(X_1 \in Z(G)) \left(1 - \frac{1}{2^{i - 1}} + \frac{1}{2^{i - 1}P(X_1 \in Z(G))} \right) \right)^{\frac{1}{n}} \\
&= \lim_{i \to \infty} P(X_1 \in Z(G))\left(1 - \frac{1}{2^{i - 1}} + \frac{1}{2^{i - 1}P(X_1 \in Z(G))} \right) \\
&= P(X_1 \in Z(G)).
\end{align*}
However, I do not know how to prove that the events in our supposition are always independent (or is there a counterexample?). And neither do I know, how to prove the main statement of the question without using the aforementioned supposition.

REPLY [2 votes]: For finite $G$, the bound given in Julian Rosen's answer is the exact limit, i.e. I claim that 
$$
\mathrm P(\forall i,j\le n,\ [X_i,X_j] = e)^{1/n}\to \max_{\text{abelian }H \le G}\frac{1}{[G:H]} = \max_{\text{abelian }H \le G}\mathrm P(X_1 \in H). \tag{$\ast$}
$$
Indeed, denoting by $\mathcal A$ the collection of abelian subgroups of $G$,
$$
\limsup_{n\to \infty} \mathrm P(\forall i,j\le n,\ [X_i,X_j] = e)^{1/n} \le \limsup_{n\to \infty}\biggl(\sum_{H\in \mathcal A} \mathrm P(\forall i\le n,\ X_i\in H)\biggr)^{1/n} =\\
= \limsup_{n\to \infty}\biggl(\sum_{H\in \mathcal A} \mathrm P(X_1\in H)^n\biggr)^{1/n} = \max_{H\in \mathcal A} \mathrm P(X_1\in H).
$$
Since by Julian Rosen's answer, 
$$
\liminf_{n\to \infty} \mathrm P(\forall i,j\le n,\ [X_i,X_j] = e)^{1/n}\ge  \max_{H\in \mathcal A}\mathrm P(X_1 \in H),
$$
we arrive at $(\ast)$.

In order for (a modification of) the argument to work, it is enough to assume that for some $n\ge 1$, $\sum_{H\in \mathcal A^*} \mathrm P(X_1\in H)^n<\infty$, where $\mathcal A^*$ is the collection of all maximal abelian subgroups of $G$.