How to accomodate a natural decay / fade out on a gated track?

I am using Sonitus:fx Gate to block low level hiss on a guitar track with a marginal S/N ratio, and it works well, except I want the last chord to decay to as close to infinity as I can get it (probably with the assistance of a fade), but when the decaying / fading signal falls below a certain threshold, the gate kicks in and the sound level either drops abruptly to infinity, or at lower gate levels the signal stutters several times as it drops past the threshold.
 
Is there a way to dynamically drop the threshold on the gate (i.e., automation) at the end of the piece to match the signal decay / fade, in order to eliminate the drop out / stutter?  Or maybe some other way of approaching the problem?
 

"However the best solution is to re-record the guitar track without hiss, if you have that option available. " +1,,,,,,, or snip the audio file at the last chord, drag the gate from the fx bin and drag it onto the audio file !!! so you'll have that part gated and the last chord can decay with out the gate kicking in

Another thing you can do for his is a low pass filter. You may find that in the context of your song, you don't actually need a considerable amount of high end as other instruments may be doing that job. If such, you might be able to get away with a LPF. I find this can work really well on a bass guitar, especially if it's a more of a dull sounding one. You might not get so much luck with a guitar, but maybe worth a look at.

My first choice would be to automate the gate threshold, but if there's a convenient split point Herb's method would work fine, too. Automating the threshold, however, gives you the option of turning the gate off or decreasing its sensitivity in other parts of the track as well.

Gee I'd just go to any ends of phrases you want a natural fade and split it there. Then clone the track and select the clip before the split and hit "Q" which is "Mute Clip" (in 8.5, Own X1 but don't use it!) and then remove the gate on the cloned track. Then mute the ends of phrases on the original track. 

Lots of times by cloning a track you can process, eq, verb, etc- just the parts of the track you want different.