No. There are examples of rv.s $X_n$ for which $\mathrm{plim}_{n\to\infty}X_n=0$ and for which $\sqrt n X_n^2 \to\infty$ (in distribution, say) and other for which $\sqrt n X_n^2\to 0$, and all sorts of wild stuff in between. Just let $X_n=\pm 1/\log n$ or $X_n = \pm1 /n!$ and so on, where (if you want) the signs are chosen randomly.