The necessary tokens for this are available to the template -- they just aren't listed in the tokens popup. In the Amount value cell, recommend we add something like:
{if $is_recur}
<br /><em> This is a recurring contribution. Your credit card or PayPal account will be charged every {$frequency_interval} {$frequency_unit}. You may cancel your recurring contribution at any time using the link provided in the receipt emailed from PayPal.</em>
{/if}
(may need to be generalized better)