So with PS4 outselling X1 by about a 2:1 margin on average or higher but with the holidays traiditonally closing the gap (not overall sales gap but weekly sales gap).  Will PS4 ever make it a 2:1 according to VGC and if so, when?

I think it'll happen sometime during Summer of next year.  Xbox has saved all its exclusives for the holidays so that will help fend it off for awhile but with all the big third party bundles for PS4 and the star wars craze incoming to help with the Battlefront association I think it'll be bigger than last year weekly sales gap wise.  PS4 has some big exclusives coming next year and since their overall category of exlusives seems to be selling it quite well during the quiet weeks I think it'll take a little while but August or Sep. next year could help make it 2:1 (I think there will be another Destiny bundle with a new expansion every year in Sep.)

According to poklane, Sony expects 38.8m PS4 shipments by March 31

If it doesn't by the end of 2016 Andrew has failed.

Also you should include the Never option. Nobody cares about 2018 yet anyway.

In April.

I voted for Q1 2016.

If it doesnt happen before holiday next year, then it is not happening ever.

even if it's only like 3 sales away after that?

Voted Q4 2016.
For everyone's information: Sony is estimating 38.8million shipped PS4s by March 31st.

thank you for that.  I'll add it to the OP

I feel like next year will be PS4 top year, but when holidays come MS have those crazy deals that will counter the 2:1 ratio sales gap overall. So they have until before holiday 2016 to make it happen. 

Q4 2016.