As someone who recently broke 3 hours in the marathon in my 60's (albeit downhill), I did a little back of the envelop calculation based on rojo's latest mile time trial at what is sounding like about 90kg.
The biggest problem facing rojo, or any other aging marathoner is that if you were say a 2:23 marathoner in your 20's/30's and you suffer the normal 10% per decade absolute VO2Max decline after 30 (which it looks like rojo has based on his PB's and mile time trial) then you have to be within about 5kg of your 20's/30's racing weight to break 3 hours in your 50's.
I'm guessing for rojo that was about 65kg, so got to drop about 20kg somehow to get down to around 70kg.