I say less than a month from the day they hit the showroom floor. I'm already bugging my wife to let me pick one up for her ski.
Yamaha did something very similar about 7 years ago in their snowmobiles. They had switched their entire lineup over to massive 4 strokes that responded very well to turbos and such. It was nothing to have 325hp 2 days after you bought your ski. After about 3 years of offering these monsters, Yamaha came out with a 90hp 500cc twin cylinder 4 stroke and brought back the Phazer. I picked up a lightly used one for my ex for $5500 out the door. It was a goofy looking thing but I ended up riding it more than she did. I had a 2003 Skidoo Summit at the time with the 800cc Rotax and 151" track. My ski was rated at 165HP but that little 4 stroke was so well balanced and engineered that it was more nimble and way more fun even though it weighed 150lbs more and had almost half the hp. It was great on fuel, near impossible to get stuck and was just an all around funner machine. They offered a turbo for it as well that would have boosted it to 135HP but I never got the chance to do it and ended up selling everything and moving to the US.
Here's a writeup on the turbo'd Phazer here;
http://www.montanayamaha.com/mcxpress_pdfs/phazer.pdf
BRP offered a fun and lightweight 2 stroke model which my boss at the time had a pair of for his kids. He bought my Phazer for his wife and said it was a much nicer ski and drank way less fuel. Even though similar in cc's and HP, the 4 stroke had way more torque which is ideal in a snowmobile.