It is tied w/ the feasts because they are a shadown of things to come, a dress rehersal, and Jesus said He came to fulfill them. The fulness of the Gentiles means from what I understand is the outpouring of the Holy Spirit. Read Is 6 and it says blindness has been given to the Jews until a certain time: when the cities lie unihabited: a massive war, I'm thinking it involves Damascus because that hasn't happened yet.
http://www.biblegateway.com/passage/?search=Isaiah%206&version=KJV
Is 30 explains this even further:
http://www.biblegateway.com/passage/?search=Isaiah%2030&version=KJV
but the most interesting part of ch 30 is this:
20 And though the Lord give you the bread of adversity, and the water of affliction, yet shall not thy teachers be removed into a corner any more, but thine eyes shall see thy teachers:
21 And thine ears shall hear a word behind thee, saying, This is the way, walk ye in it, when ye turn to the right hand, and when ye turn to the left.
After war; desolation they will see their 'teachers', this is the fulness of the gentiles.
kari