Actually, for me the bigger surprise this year is the addition of a 1/35 range of armoured vehicles, which is not exactly something Airfix is known for - iirc, most of the armoured vehicles up to now were in the 1/32 range, and while some are 'the usual suspects' (i.e. Panzer IV, Panther, Tiger, Sherman and T-34) that none the less will be welcome, others are very nice and surprising additions indeed (I can't recall too many kits of the LT.35/Pz.Kpfw 35(t) or of the M-36 Jackson, and the little tractor has me intrigued!)
The MiG-17 makes for a wonderful addition to any range, as it is an aircraft type that is not often seen in this scale - other than the vintage KP kit of the early 1970s and the Hasegawa one from the same era - both covering the radar-equiped version; the Dragon kit from the 1990s with numerous shape issues; and the recent but difficult to build entry by AZ, it seems to have been somewhat ignored (most manufacturers going for either the Korea-era Mig-15, or the Vietnam-era MiG-21) despite its important role in a number of conflicts, especially those in the Middle East and Vietnam of course!
Of course, the 'why' mostly seems to stem from it appearing in the releases list instead of a newly moulded Brit (de Havilland Venom, anybody?) but that doesn't mean it's any less welcome!