https://buy.garmin.com/us-us/us/p/560327

Why would it not? I can't think of any reason that the new flagship watch wouldn't support the latest IQ version. The only, stated, reason that the F3 isn't getting IQ 2 is because of the processing power and the F5 series certainly has a stronger chip in it. I don't have time right now to look it up but I'm pretty sure that there was a passing mention of it in DCRaimkers hands on post.
While Garmin's specs appear to indicate the Fenix 3HR and 5X are the same physical size, from the early looks it appears that the 3 HR is really the same as the 5, and the 5X is significantly larger and heavier than even the 3 HR.
joesahfeen,
9 times out of 10 my sync occurs over bluetooth, but every now and then it takes too long, or fails outright. If I'm in my home I'll just trigger a wifi sync instead and that usually takes care of it. If I'm traveling then I'm basically out of luck until I can fix the bluetooth connection. Wifi on Garmin devices needs to be pre-configured to a known wifi access point through Garmin Express, so for some it has limited appeal since you can't just configure it for any wifi router on the device itself. If that ever changes then I think it might have more appeal.