Goals: Is a 50K in my future?

Now that's just silly, isn't it?   A 50k?!  I haven't even completed a half-marathon yet.  What makes me think I  can skip right over the standard marathon and dive into a 50k?

I plan on doing a half-marathon before this year is up.  That means I have 4 months.  I will do it, but it's a matter of choosing the right one.  I think I am going to do only long trail races from hereon out and some short road races. To me a short road race is a 10 - 15k or less. Half marathons, marathons, 25ks etc will be on trails only.  I do this for a couple of reasons.

1. I will always run on roads.Probably more than half my mileage will be on roads.  I can work on speed on the roads.
2. Trail races, typically being longer races in general, are normally easier on the joints for me.  I may as well do my long races on easier surfaces.