Gibbs' inequality is equivalent to:
\begin{equation} \sum_{i} \ln q_i^{p_i}-\ln p_i^{p_i} \leq 0 \end{equation}
where $p_i,q_i \in [0,1]$ and $\sum_i p_i = \sum_i q_i=1$.
Now, a friend of mine suggested that assuming $p_i,q_i \in [0,1]$ and $\sum_i p_i = \sum_i q_i=1$, Gibbs' inequality implies:
\begin{equation} \sum_{i} q_i^{p_i}-p_i^{p_i} \leq 0 \end{equation}
Right now I doubt this is true but I can't think of a counter-example.
Update: I have found experimental evidence for my friends' conjecture by running the following Python code:
import numpy as np
count = 0
for i in range(10000):
# randomly create distributions:
P, Q = np.random.rand(10), np.random.rand(10)
p, q = P/np.sum(P), Q/np.sum(Q)
M = np.sum([p[i]**p[i] for i in range(10)])
m = np.sum([q[i]**p[i] for i in range(10)])
if m <= M:
count+=1
The inequality was satisfied every single time I ran this script.