After averaging about 60 miles/week for the last 4 years I've now taken 3 straight months off with almost no running. How long will it take to get back in good shape? By good shape I mean roughly 16 min for 5k (PR is 15:20)? Also, will taking 3 months off have any implications 6 months from now?[/quote]
Depends on a number of factors. First, some people get fit more quickly than others.
As far as an answer to your question, there is no way to tell, except for just start your training and see where you are in 2 months.
Other things to consider:
How much weight did you gain over your previous racing weight?
How long does it usually take you to get into shape after a short layoff?
Bottom line: Be smart about your training, and don't be afraid to push to get to where you were.